Blog

  • How do I crimp automotive wire connectors properly?

    Quick answer

    Pick a terminal sized for your cable’s copper area in mm² (not its “mm” label), strip just enough insulation to fill the terminal barrel, and crimp it with a ratchet crimper using the die that matches the terminal. A good crimp passes a hard tug test without the wire moving. Finish with adhesive-lined heat shrink wherever the joint will see water, dust or vibration.

    Is this a DIY job?

    • Difficulty: Easy
    • Time: 2 to 5 minutes per terminal once you’re set up
    • Tools: ratchet crimper with the right dies, wire stripper, side cutters, heat gun
    • Skills: none beyond care and patience; practise on offcuts first

    Crimping is one of the most useful skills for any 12V job, and a good tool does most of the work. Leave it to a professional if the terminals are part of a factory loom connector, an airbag circuit, or anything high-current like starter or winch cables.

    Step by step

    1. Make it safe. If the wire is connected to anything live, pull the circuit’s fuse or disconnect the battery first: negative off first, and negative back on last when you’re done.
    2. Check the cable size in mm². Read the printing on the cable, or check the reel. Australian auto cable sold as “3mm” has about 1.13 mm² of copper, “4mm” about 1.84 mm² and “6mm” about 4.59 mm². (see What size cable do I need for my 12V accessory?)
    3. Choose a terminal that suits that copper area. Insulated terminals are colour-coded by wire range (see the table below). For a sealed, tidy job, choose terminals with a nylon sleeve or plan to use heat shrink. Use stranded auto cable; solid-core wire isn’t suited to crimp terminals.
    4. Slide on the heat shrink first. It’s easy to forget, and once the terminal is on you can’t add it.
    5. Strip the insulation. Remove only enough to fill the metal barrel of the terminal. Use a stripper set to the right size so you don’t cut or nick strands. Twist the strands lightly so none stray.
    6. Insert the wire. Push the bare copper fully into the barrel. On an insulated terminal, the end of the insulation should sit just inside the plastic sleeve. On an open-barrel (non-insulated) terminal, the copper sits under the larger front tabs and the insulation sits under the smaller rear tabs, with a few strand ends just visible past the front tabs.
    7. Use the matching die. Put the terminal in the die that matches its colour or size. Insulated terminals and open-barrel terminals need different dies; one die won’t do both properly.
    8. Crimp in one full stroke. Squeeze the ratchet crimper until it releases by itself. The ratchet stops you letting go half way, which is the most common cause of loose crimps.
    9. Tug test it. Hold the terminal and pull the wire firmly. It must not slide, rotate or pull out. If it moves, cut it off and start again; don’t re-crimp the same terminal.
    10. Inspect it. You shouldn’t see loose strands outside the barrel, insulation trapped under the copper crimp, or a cracked sleeve.
    11. Seal it. Slide the adhesive-lined heat shrink over the barrel and onto the cable insulation, then heat it evenly until it shrinks and a little adhesive shows at each end.
    12. Restore power and test. Refit the fuse or reconnect the battery (negative last) and check the circuit works.

    Specs table

    Insulated terminal colours and Australian auto cable

    The colour code on insulated crimp terminals is widely used across makers. Always check the wire range printed on the packet.

    Terminal colour Wire range Australian auto cable that fits
    Red 0.5 to 1.5 mm² 3mm auto cable (1.13 mm²)
    Blue 1.5 to 2.5 mm² 4mm auto cable (1.84 mm²)
    Yellow 4 to 6 mm² 5mm (2.90 mm²) and 6mm (4.59 mm²) auto cable

    Note: 5mm auto cable (2.90 mm²) is too big for blue terminals, so auto electricians use yellow. It sits at the small end of the yellow range, so use a good ratchet crimper on the yellow die and always pull-test the crimp firmly. Some terminal makers print a wider yellow range, so check the packet.

    Heavier cable (8 B&S and up) uses tubular copper lugs crimped with a hex or hydraulic lug crimper, not these terminals.

    How strong is a good crimp?

    For reference, the UL 486A standard sets minimum pull-out forces for crimped terminals. A good crimp should comfortably beat a firm hand tug.

    Wire size Approx. copper area UL 486A minimum pull-out
    18 AWG 0.82 mm² 89 N (about 9 kg)
    16 AWG 1.31 mm² 133 N (about 13.6 kg)
    14 AWG 2.08 mm² 222 N (about 22.7 kg)
    12 AWG 3.31 mm² 311 N (about 31.8 kg)

    These figures are a guide to how much a sound crimp should hold. A home tug test can’t measure them, but a crimp that pulls out by hand is well short.

    What you’ll need

    • ratchet crimper insulated terminals
    • ratchet crimper non-insulated terminals (if you use open-barrel terminals)
    • automatic wire stripper
    • insulated crimp terminal kit
    • heat shrink crimp terminals (for wet or exposed locations)
    • adhesive lined heat shrink
    • heat gun
    • auto cable (sized for the job)

    When to call an auto electrician

    • The terminals are inside a factory connector plug. These need the correct pin, seal and often a dedicated crimp tool.
    • The wiring is near airbags, seatbelt pretensioners or their yellow looms. Airbag (SRS) wiring is professional-only.
    • The vehicle is a hybrid or electric vehicle and the cable is orange. High-voltage systems are professional-only.
    • You need to terminate heavy battery, starter, winch or inverter cable.
    • A crimped joint is getting hot, discoloured or causing a fault that comes and goes.

    Need an auto electrician? Find local auto electricians and mobile services in your city.

    Find an auto electrician near you

    Related questions

    Q: Can I crimp terminals with pliers? A: You can squash a terminal with pliers, but it won’t compress evenly and often loosens with vibration. A ratchet crimper with the right die makes a consistent crimp every time.

    Q: Should I solder a crimp as well? A: It depends on the job. Many auto electricians see a soldered and crimped joint as the best for conductivity and long life, but a correct crimp made with the right tool is reliable on its own for most jobs. If you do solder, keep the solder to the crimped area and support the cable behind the terminal, because solder that wicks up the strands makes a stiff spot where vibration can crack the wire. Sealed connectors such as Deutsch use solid contacts with a four-indent crimp and normally aren’t soldered.

    Q: What does the colour on a crimp terminal mean? A: It shows the wire size the terminal suits: red for 0.5 to 1.5 mm², blue for 1.5 to 2.5 mm² and yellow for 4 to 6 mm².

    Q: Do I need heat shrink over crimp terminals? A: Inside the cabin it’s optional on insulated terminals. Under the bonnet, under the vehicle, on a trailer or anywhere wet, adhesive-lined heat shrink keeps water and corrosion out of the joint.

    Q: How do I connect a new accessory to power safely? A: Run it from a fused source, with the fuse close to the battery and rated to protect the cable. (see Where should the fuse go when wiring an accessory?)

    Sources

    1. RS Components (RND Connect), insulated crimp terminal datasheet – colour code red 0.5–1.5 mm² (22–16 AWG), blue 1.5–2.5 mm² (16–14 AWG), yellow 4–6 mm² (12–10 AWG). https://docs.rs-online.com/c5cd/A700000013591123.pdf (checked October 2026)
    2. Tycab, automotive cable catalogue – single-core auto cable stranding and copper areas (14/0.32 1.13 mm², 23/0.32 1.84 mm², 36/0.32 2.90 mm², 57/0.32 4.59 mm²). https://www.tyree.nz/wp-content/uploads/2019/09/Automotive-Comp.pdf (checked October 2026)
    3. Molex, “Introduction to Crimp Technology” (application tooling) – parts of a crimp (conductor crimp, insulation crimp, bellmouth, conductor brush), common defects, pull testing. https://www.molex.com/content/dam/molex/molex-dot-com/en_us/pdf/general/987652-5181.pdf (checked October 2026)
    4. NASA, NASA-STD-8739.4A “Workmanship Standard for Crimping, Interconnecting Cables, Harnesses, and Wiring” – stranded wire for crimped contacts; full-cycle ratcheting crimp tools; pull testing. https://nepp.nasa.gov/files/27631/nstd87394a.pdf (checked October 2026)
    5. Cirris, “Crimp pull testers: pullout force per wire size” – summary of UL 486A minimum pull-out forces for terminals (18 AWG 20 lbf, 16 AWG 30 lbf, 14 AWG 50 lbf, 12 AWG 70 lbf; converted to newtons and kg). https://cirris.com/crimp-pull-testers-pullout-force-per-wire-size/ (checked October 2026)
    6. AWG to mm² conversions (18 AWG 0.82 mm², 16 AWG 1.31 mm², 14 AWG 2.08 mm², 12 AWG 3.31 mm²) – standard American Wire Gauge definitions.
    7. Hella, heat shrink insulated crimp terminal connectors – red, blue and yellow terminals, with yellow for 4 to 6 mm² cable. https://www.hella.co.nz/en/products/accessories/connectors/heat-shrink-insulated-crimp-terminal-connector.html (checked October 2026)
    8. Wiltronics, 4mm twin core auto cable – “4mm” auto cable is 23/0.32 stranding (about 1.85 mm²). https://www.wiltronics.com.au/product/52830/4mm-twin-core-auto-cable (checked October 2026)

  • How much solar do I need for my caravan?

    Quick answer

    Work out how much power you use in a day, then size your solar to replace it, with a margin for cloudy days and less-than-ideal panel angles. Panels rarely produce their full rated output: shading, heat, dust, panel angle, time of year and where you are in Australia all reduce it. A common planning approach is to estimate daily solar harvest as panel watts × an assumed number of peak sun hours × a system efficiency factor, then compare it with your daily use. Your battery size decides how long you can last when the sun doesn’t cooperate.

    Is this a DIY job?

    • Difficulty: Easy to calculate; Medium to install portable panels; Pro for roof-mounted panels, regulators and wiring into an existing system
    • Time: 30 minutes to work out
    • Tools: appliance labels or manuals, a battery monitor (if you have one), calculator
    • Skills: simple maths

    Step by step

    1. List your 12V appliances. Fridge, lights, water pump, fans, USB charging, diesel heater, TV, and anything run through an inverter.
    2. Find each one’s power draw. Look for amps (A) or watts (W) on the label or in the manual. For 12V, amps ≈ watts ÷ 12.
    3. Estimate hours of use per day. A fridge cycles on and off, so use the maker’s daily energy figure if it gives one, or measure it with a battery monitor.
    4. Work out daily use in amp-hours (Ah). For each appliance: amps × hours per day. Add them up.
    5. Add inverter losses. Anything run through an inverter uses more than its rated power from the battery. Allow extra, or check the inverter maker’s efficiency figure. (see How do I choose and install an inverter?)
    6. Estimate daily solar harvest. For planning: panel watts ÷ 12 × assumed peak sun hours × efficiency factor = Ah per day. The peak sun hours you can expect depend on location and season; use a conservative figure for winter or southern trips. An efficiency factor (for heat, dust, angle and cable and regulator losses) is often assumed to be around 0.7, but treat it as a rough guide.
    7. Compare and add a margin. Your solar harvest on a typical day should comfortably exceed your daily use if you want to stay put. Cloudy days can produce much less.
    8. Size the battery for the gap. Battery capacity covers nights and cloudy days. Lithium lets you use more of its rated capacity than AGM.
    9. Choose a suitable regulator. MPPT regulators generally get more from the panels than PWM regulators, especially in low light and on larger systems. PWM can suit a small system on a budget. Many DC-DC chargers include one. (see DC-DC charger or VSR isolator: which do I need?)
    10. Check with real numbers. Once set up, a battery monitor shows what you actually use and harvest. Adjust from there.

    Specs table

    Worked example (illustration only, not a recommendation)

    Item Draw Hours/day Ah/day
    12V compressor fridge (average) 2.5 A 24 (average, including cycling) 60
    LED lights 2 A 4 8
    Water pump 5 A 0.5 2.5
    USB devices 2 A 3 6
    Total about 77 Ah

    Solar estimate using the planning formula, assuming 5 peak sun hours and an efficiency factor of 0.7:

    Panel size Estimated Ah/day
    200 W 200 ÷ 12 × 5 × 0.7 ≈ 58 Ah
    300 W ≈ 88 Ah
    400 W ≈ 117 Ah

    In this example, 200 W wouldn’t keep up on a good day; 300 W would cover the daily use with a small margin; 400 W gives more room for cloud or extra loads. Fewer sun hours (for example in winter) reduce every figure. Your own appliance draws and conditions will differ.

    What you’ll need

    • solar panel 12V or portable folding solar panel
    • MPPT solar regulator (or a DC-DC charger with solar input)
    • Anderson plug 50A and solar extension lead
    • battery monitor
    • inline fuse holder / circuit breaker

    When to call an auto electrician

    • You’re installing roof panels and running cable into the van.
    • You’re adding solar to a system with a DC-DC charger, lithium battery or inverter.
    • The battery isn’t charging as expected from solar.
    • Any 240V work. Fixed 240V wiring in a caravan must be done by a licensed electrician.

    Need an auto electrician? Find local auto electricians and mobile services in your city.

    Find an auto electrician near you

    Related questions

    Q: Portable or roof-mounted solar? A: Roof panels are always connected and need no setting up. Portable panels can be aimed at the sun and placed in sun while the van is in shade. Many people use both.

    Q: Why am I getting less solar than my panels are rated for? A: Panel ratings are measured in ideal lab conditions. Heat, angle, dust, shading, time of year and cable losses all reduce real output.

    Q: Do I need an MPPT regulator? A: It’s not essential, but MPPT generally harvests more energy than PWM. Many DC-DC chargers have MPPT built in.

    Q: How long will my battery last without sun? A: Divide the battery’s usable capacity by your daily use, after allowing for any partial solar. Lithium lets you use more of its rated capacity than AGM.

    Sources

    1. Signature Camper Trailers, “How much solar do you need?” – planning formula (panel watts ÷ 12 × 5 peak sun hours × 0.7 efficiency); daily use in Ah; cloudy-day reduction (manufacturer guide; assumptions not independently sourced). https://signaturecampertrailers.com.au/how-much-solar-do-you-need/ (checked October 2026)
    2. REDARC, “Regulating the sun” – MPPT regulators harvest more from the panels, especially in low light and on larger systems; PWM suits small, budget systems. https://www.redarcelectronics.com/au/discover/regulating-the-sun/ (checked October 2026)
    3. WorkSafe ACT, “Electrical incident” – 240V installations in caravans and transportable structures should be done by a licensed electrician and certified to AS/NZS 3001. https://www.worksafe.act.gov.au/health-and-safety-portal/safety-alerts/electrical-incident (checked October 2026)
    4. Consumer, Building and Occupational Services Tasmania, “Using electricity safely in caravans and tents” – don’t do DIY electrical work on a caravan; only a licensed electrician can. https://cbos.tas.gov.au/topics/technical-regulation/electrical-standard-safety/using-electricity-safely-in-caravans-and-tents (checked October 2026)

  • DC-DC charger or VSR isolator: which do I need?

    Quick answer

    A VSR (voltage sensitive relay, or isolator) simply connects your auxiliary battery to the vehicle’s charging system when the engine is running. A DC-DC charger converts the vehicle’s power into a proper multi-stage charge for the auxiliary battery. Choose a DC-DC charger if your vehicle has a smart (variable-voltage) alternator, your auxiliary battery is lithium, the cable run is long (canopy, tray or caravan), or you want solar charging built in. A VSR can still suit an older vehicle with matching lead-acid batteries close together under the bonnet.

    Is this a DIY job?

    • Difficulty: Medium for a VSR under the bonnet; Pro for a DC-DC charger with long cable runs, lithium or a smart alternator
    • Time: 2 to 6 hours
    • Tools: heavy cable crimper, cable cutter, multimeter, drill and grommets
    • Skills: high-current wiring and fusing

    Step by step: choosing

    Dual battery system overview The alternator charges the starting battery. A charging device, either a VSR or a DC-DC charger, links the starting battery to the auxiliary battery, with a fuse or circuit breaker near each battery. Solar can feed the auxiliary battery through a regulator or the DC-DC charger. Accessories such as the fridge and lights run from the auxiliary battery through a fuse block. How a dual battery system works Alternator engine running Starting battery starts the engine, runs the vehicle Charging device VSR (isolator) or DC-DC charger Auxiliary battery deep-cycle AGM or lithium securely mounted Fuse block one fuse per accessory Solar panel via regulator or the DC-DC solar input Fridge Lights, USB fuse fuse Key points Fuse or circuit breaker close to each battery. Engine off: batteries are separated, so accessories can’t flatten the starting battery. Smart alternator, lithium or long cable run: a DC-DC charger is usually the better choice.
    Dual battery system overview showing where the VSR or DC-DC charger sits
    1. Find out what alternator you have. Many newer vehicles (roughly 2015 on, and some older ones) have smart or variable-voltage alternators, often alongside stop-start or a battery sensor on the negative terminal. Check the owner’s manual or ask the vehicle maker. A smart alternator may drop its output once the starting battery is full, so a VSR may not see enough voltage to charge the auxiliary battery properly.
    2. Check your auxiliary battery type. Lithium (LiFePO4) batteries need a charge profile to suit them. A DC-DC charger with a lithium setting is the usual choice. A VSR generally suits matching lead-acid batteries.
    3. Measure the cable run. Long cables lose voltage. A DC-DC charger mounted near the auxiliary battery makes up for some of that loss. A VSR can’t, so the auxiliary battery may only partly charge. (see What size cable do I need for my 12V accessory?)
    4. Decide on solar. Many DC-DC chargers have a built-in solar input (often MPPT). With a VSR, you need a separate solar regulator.
    5. Consider cost and simplicity. A VSR is simpler and cheaper. A DC-DC charger costs more but usually charges more completely.
    6. Check the charger’s input rules. Some DC-DC chargers need an ignition or “D+” signal to work with smart alternators. Follow the maker’s instructions.
    7. Fuse both ends. Fit a fuse or circuit breaker near the starting battery and near the auxiliary battery (or at the charger output), sized for the cable.

    Specs table

    Situation Usually suits
    Older vehicle, conventional alternator, two lead-acid batteries side by side VSR
    Smart or variable-voltage alternator DC-DC charger
    Lithium auxiliary battery DC-DC charger with lithium profile
    Auxiliary battery in a canopy, tray or caravan (long run) DC-DC charger near the auxiliary battery
    Want solar charging through the same unit DC-DC charger with solar input
    Lowest cost, simplest install VSR (if the situation above suits)

    What you’ll need

    • DC-DC charger or voltage sensitive relay
    • heavy duty single core auto cable or twin core auto cable
    • circuit breaker / MIDI fuse holder (one each end)
    • cable lugs and adhesive heat shrink
    • Anderson plug 50A (for caravan or trailer connections)

    When to call an auto electrician

    • Your vehicle has a smart alternator, a battery sensor, stop-start or a battery management system.
    • You’re installing a lithium battery or running cable to a canopy, tray or caravan.
    • The auxiliary battery isn’t fully charging after a day’s driving.
    • You want a combined system with solar, an inverter and a battery monitor.

    Need an auto electrician? Find local auto electricians and mobile services in your city.

    Find an auto electrician near you

    Related questions

    Q: Can I use a VSR with a lithium auxiliary battery? A: Generally not recommended. Lithium batteries need a suitable charge profile, and they can draw very high current from the alternator through a VSR. A DC-DC charger with a lithium setting is the usual approach.

    Q: How do I know if I have a smart alternator? A: Signs include stop-start, a sensor on the battery negative terminal, or charging voltage that varies a lot while driving. Check the owner’s manual or ask the vehicle maker. (see What is a smart alternator and how does it affect accessories?)

    Q: Does a DC-DC charger need solar? A: No. Solar input is an option on many units. It’s useful if you camp for several days without driving.

    Q: Where should the DC-DC charger go? A: Usually close to the auxiliary battery, with heavy cable from the vehicle side. Follow the maker’s limits on heat and mounting.

    Sources

    1. REDARC, “Choosing the right charger for a dual battery system” – isolators connect on sensed voltage and rely on alternator output; DC-DC chargers set the charge to suit the battery and handle voltage drop to a canopy better; isolators generally suit older fixed-voltage vehicles, DC-DC chargers newer variable-voltage ones; solar input. https://www.redarcelectronics.com/au/discover/choosing-the-right-charger-for-a-dual-battery-system/ (checked October 2026)
    2. REDARC, “BCDC v DC-DC dual battery chargers” – variable-voltage (smart) alternators need a DC-DC charger for the auxiliary battery; chemistry-specific charge profiles including lithium; solar charging. https://www.redarcelectronics.com/au/discover/bcdc-v-dcdc-dual-battery-chargers/ (checked October 2026)

  • Where should the fuse go when wiring an accessory?

    Quick answer

    Put the fuse in the positive cable as close to the battery (or other power source) as practical, so almost none of the cable is left unprotected. Rate the fuse at or below what the cable can safely carry, and above what the accessory normally draws. The fuse’s job is to protect the cable from overheating if it shorts to the body, which is why it belongs at the source end, not at the accessory.

    Is this a DIY job?

    • Difficulty: Easy
    • Time: 15 to 45 minutes, depending on access to the battery
    • Tools: spanners for the battery terminals, crimp tool, wire stripper, multimeter, cable ties
    • Skills: basic crimping and reading a current rating

    Fitting a fuse holder is straightforward. Get help if you’re feeding high-current gear (inverters, winches, DC-DC chargers), working on a vehicle with a battery monitoring sensor on the negative terminal, or wiring anything in a hybrid or electric vehicle.

    Step by step

    1. Work out the accessory’s current. Check its label or manual for amps. If it only lists watts, divide by 12 for a rough figure (for example, 120 W ÷ 12 V = 10 A).
    2. Size the cable first. Choose cable by copper area in mm² for the current and run length. The fuse is chosen to suit the cable, so this comes first. (see What size cable do I need for my 12V accessory?)
    3. Pick the fuse rating. It must be above the accessory’s normal draw (including any start-up surge the maker mentions) and at or below the cable’s current rating. If the accessory maker specifies a fuse, use that, as long as it’s no higher than the cable can carry.
    4. Pick the fuse type. Getting the protection right matters more than anything else in this job, because it’s what stops cable damage and fires. Blade fuses suit most small accessories. Higher currents need MIDI or ANL fuses, or a circuit breaker (see the table below). Under the bonnet, under the vehicle or anywhere it can get wet, use a waterproof (sealed) fuse holder or circuit breaker. A circuit breaker can be reset instead of replaced, which suits accessory circuits that may trip occasionally.
    5. Disconnect the battery. Negative terminal off first, then you can work near the positive safely.
    6. Mount the fuse holder close to the battery. Fix it firmly, away from sharp edges, exhaust heat and moving parts, and where you can reach it to check or replace the fuse. The short cable between the battery and the fuse is the only unprotected part, so keep it as short as you practically can and protect it with loom tube.
    7. Connect the battery side. Use a properly crimped lug on the battery positive terminal or an approved power stud. Don’t stack lots of lugs on one terminal.
    8. Run the cable to the accessory. Use loom tube, grommets through any metal panel, and secure it every so often so it can’t rub through.
    9. Run a proper earth. Use a negative cable of the same size back to the battery or a clean, solid chassis earth point.
    10. Fit the fuse last. With everything connected and checked, fit the fuse, then reconnect the battery: negative on last.
    11. Test. Switch the accessory on and confirm it works. Check that nothing, including the fuse holder, gets warm after a few minutes of running.

    Two power sources, two fuses. If a cable can be fed from both ends, such as the link cable between a main and an auxiliary battery, or the feed to a DC-DC charger, fit a fuse or circuit breaker near each battery. A short anywhere along the cable is then cut off from both sides. (see How does a dual battery system work and do I need one?)

    Specs table

    Common fuse and breaker types for 12V accessories

    Type Typical ratings Notes
    Standard or mini blade fuse Up to 40 A Colour-coded by rating; plugs into an inline holder or fuse block
    MIDI (bolt-down) fuse 30 to 200 A (32 V DC) Time-delay type that tolerates short surges; the maker states 150 to 200 A sizes are for short-circuit protection only
    ANL fuse 35 to 750 A Bolt-on, for heavy cables such as inverter and winch feeds
    Circuit breaker, Type I (auto reset) Various Resets itself and keeps cycling until the fault clears
    Circuit breaker, Type II (modified reset) Various Stays open while power is applied; resets when power is removed
    Circuit breaker, Type III (manual reset) Various Stays off until you press the reset button or lever

    For accessory feeds, a manual-reset (Type III) breaker is usually the safer choice, because it stays off until someone looks at why it tripped.

    Blade fuse colours

    Rating Colour
    5 A Tan
    7.5 A Brown
    10 A Red
    15 A Blue
    20 A Yellow
    25 A Clear (natural)
    30 A Green
    40 A Orange

    Maxi fuses use a different colour code. Always go by the number printed on the fuse.

    Matching fuse to cable (examples)

    Cable ratings from one Australian cable maker, for a single cable at 30°C. Ratings drop with heat and bundling, so in an engine bay choose a fuse well under the figure.

    Cable sold as Copper area Maker’s rating at 30°C Fuse must be no higher than
    3mm auto cable 1.13 mm² 20 A 20 A, lower in hot spots
    4mm auto cable 1.84 mm² 28 A 28 A, lower in hot spots
    6mm auto cable 4.59 mm² 48 A 48 A, lower in hot spots

    Fuses come in set ratings, so choose the nearest standard size at or below the limit. Twin-core and bundled cables have lower ratings than single-core; check the figure for the exact cable you buy.

    Other brands rate the same sizes much lower. For example, some 3mm auto cable sold in Australia is rated at 10 A, and some 4mm twin-core at 15 A. Go by the rating printed on the cable or packet you actually buy, and if in doubt use the lower figure.

    What you’ll need

    • inline blade fuse holder (waterproof type under the bonnet)
    • blade fuses
    • MIDI fuse holder or ANL fuse holder (high-current feeds)
    • manual reset circuit breaker
    • fuse block (if you’re adding several accessories)
    • cable lugs and crimp terminals
    • split loom tube and rubber grommets
    • auto cable (sized for the job)

    When to call an auto electrician

    • The accessory draws high current (inverter, winch, air compressor, DC-DC charger) or needs cable heavier than 6mm auto cable.
    • The vehicle has a battery sensor on the negative terminal, a smart alternator, or a stop-start system. Adding loads in the wrong place can upset charging. (see What is a smart alternator and how does it affect accessories?)
    • You’re adding several accessories and need a fused distribution block or auxiliary battery.
    • Fuses keep blowing. That usually points to a short or a fault, not a fuse that’s too small.
    • The vehicle is a hybrid or EV (high-voltage systems are professional-only), or the wiring runs near airbags or SRS looms.

    Need an auto electrician? Find local auto electricians and mobile services in your city.

    Find an auto electrician near you

    Related questions

    Q: Should the fuse go near the battery or near the accessory? A: Near the battery. A short can happen anywhere along the cable, and only the part after the fuse is protected.

    Q: Can I use a bigger fuse so it stops blowing? A: No. A fuse rated higher than the cable lets the cable overheat before the fuse blows. Find out why it’s blowing instead.

    Q: Does the negative cable need a fuse? A: In a normal negative-earth vehicle, the fuse goes in the positive cable only. The negative is at earth potential, so a short to the body doesn’t draw current through it.

    Q: Can I tap into the vehicle’s fuse box instead? A: For small loads, a fuse tap on a suitable circuit can work. Stay within that circuit’s rating and avoid safety circuits such as airbags.

    Q: Fuse or circuit breaker: which is better? A: Both protect the cable. A breaker can be reset after a trip; a fuse is cheaper and simpler. For high currents, choose a type rated for the job.

    Sources

    1. Tycab, automotive cable catalogue – low tension single-core cable by stranding, with copper areas and current ratings at 30°C (14/0.32 1.13 mm² 20 A; 23/0.32 1.84 mm² 28 A; 57/0.32 4.59 mm² 48 A) and temperature derating. https://www.tyree.nz/wp-content/uploads/2019/09/Automotive-Comp.pdf (checked October 2026)
    2. Littelfuse, ATO and MAXI blade fuse datasheet (via Farnell) – blade fuse colour codes by rating; maxi colour code differs. https://www.farnell.com/datasheets/82316.pdf (checked October 2026)
    3. Littelfuse, MIDI 498 series datasheet – 32 V DC, 30 to 200 A, time-delay; 150 to 200 A for short-circuit protection only. https://www.enika.eu/data/files/Littelfuse_MIDI_0498_auto32V.pdf (checked October 2026)
    4. Eaton Bussmann, ANL low-voltage limiter fuse datasheet – 35 to 750 A, 32 V AC / 80 V DC. https://static.chipdip.ru/lib/651/DOC044651693.pdf (checked October 2026)
    5. Littelfuse, aftermarket circuit breakers catalogue – Type I automatic reset, Type II modified reset, Type III manual reset definitions. https://www.littelfuse.com/~/media/automotive/datasheets/circuit-breakers/littelfuse_aftermarket_circuit_breakers.pdf (checked October 2026)
    6. Narva, 3mm single core cable – sold as 3mm and rated 10 A. https://narva.com.au/products/narva-10a-3mm-white-single-core-cable-100m (checked October 2026)
    7. Wiltronics, 4mm twin core auto cable – 23/0.32 stranding, 1.85 mm², rated 15 A. https://www.wiltronics.com.au/product/52830/4mm-twin-core-auto-cable (checked October 2026)

  • What size cable do I need for my 12V accessory?

    Quick answer

    Cable size depends on two things: the current the accessory draws and the total length of the cable run (there and back). At 12V, even a small voltage loss matters, so long runs need much thicker cable than you’d expect. Always compare cable by its copper area in mm², not its “mm” label: a cable sold as “6mm auto cable” has roughly 4.6 mm² of copper, not 6 mm². Then fuse the cable close to the battery so the fuse protects the cable.

    Is this a DIY job?

    • Difficulty: Medium
    • Time: 15 minutes to work out
    • Tools: accessory’s current rating (from its label or manual), tape measure, the table below
    • Skills: simple maths

    Step by step

    1. Find the current. Check the accessory’s label or manual for amps (A). If it only gives watts, divide by 12 for a rough figure (for example, 60 W ÷ 12 V = 5 A).
    2. Measure the run. Measure the one-way distance from the battery (or fuse block) to the accessory, along the route the cable will actually take.
    3. Decide the acceptable voltage drop. Many installers aim to lose no more than about 3% (around 0.36 V on a 12V system). Charging circuits such as DC-DC chargers and fridges often perform better with less: check the maker’s instructions, which usually specify a cable size.
    4. Look up the table below. Find your current and pick a cable whose maximum length is longer than your one-way run.
    5. Check the cable’s current rating. The table only covers voltage drop. The cable must also be rated for the current: use the ratings table below or the maker’s figure, and reduce it for heat and bundling.
    6. Choose the fuse. Fit a fuse or circuit breaker close to the battery, rated to protect the cable (at or below the cable’s rating) and suitable for the accessory. (see Where should the fuse go when wiring an accessory?)
    7. Use twin-core or a proper return. The negative needs the same size as the positive if it runs back to the battery. A thin earth wire undoes a thick positive cable.

    Specs table

    Auto cable labels, copper area and current rating

    The “mm” in an auto cable’s name is roughly its outside size, not its copper. What carries the current is the conductor cross-section in mm². Tycab, a major Australian cable maker, publishes these figures for its single-core auto cable:

    Sold as Stranding Copper area Tycab current rating at 30°C
    3mm auto cable 14/0.32 1.13 mm² 20 A
    4mm auto cable 23/0.32 1.84 mm² 28 A
    5mm auto cable 36/0.32 2.90 mm² 37 A
    6mm auto cable 57/0.32 4.59 mm² 48 A

    Heavier cable (B&S)

    B&S is the Australian name for the American wire gauge (AWG) sizes, but Australian battery cable is often made a little lighter than the true AWG area. Compare mm², not the gauge number.

    Size True AWG area Tycab battery cable area Tycab current rating at 30°C
    8 B&S 8.37 mm² 7.71 mm² 74 A
    6 B&S 13.3 mm² 13.5 mm² 103 A
    4 B&S 21.2 mm² 20.26 mm² 135 A
    2 B&S 33.6 mm² 32.07 mm² 188 A
    0 B&S 53.5 mm² 49.0 mm² 246 A

    Ratings drop with heat and bundling. Tycab’s ratings are for a single cable at 30°C. In hotter places, multiply by Tycab’s derating factor: 0.9 at 40°C, 0.76 at 50°C, 0.60 at 60°C and 0.45 at 70°C. A 6mm cable rated at 48 A carries only about 29 A in a 60°C engine bay. Cables bundled together in a loom lose more again. Twin-core cable is rated lower than single-core of the same size for the same reason; check the rating for the exact cable you buy.

    Maximum one-way run for about 3% voltage drop at 12V (copper, 20°C)

    Cable 5 A 10 A 20 A 30 A 50 A 100 A
    3mm auto (1.13 mm²) 2.4 m 1.2 m too small too small too small too small
    4mm auto (1.84 mm²) 3.9 m 1.9 m 1.0 m too small too small too small
    5mm auto (2.90 mm²) 6.1 m 3.0 m 1.5 m too small too small too small
    6mm auto (4.59 mm²) 9.6 m 4.8 m 2.4 m 1.6 m too small too small
    8 B&S (8.37 mm²) 17.5 m 8.8 m 4.4 m 2.9 m 1.8 m too small
    6 B&S (13.3 mm²) 27.8 m 13.9 m 7.0 m 4.6 m 2.8 m too small
    4 B&S (21.2 mm²) – 22.2 m 11.1 m 7.4 m 4.4 m 2.2 m
    2 B&S (33.6 mm²) – – 17.6 m 11.7 m 7.0 m 3.5 m
    0 B&S (53.5 mm²) – – 28.0 m 18.7 m 11.2 m 5.6 m

    How the table is worked out: voltage drop = current × resistance of the full loop (out and back). Copper resistance is about 0.0172 ohm per metre for 1 mm² at 20°C. Real cable gets warmer and loses a little more. B&S rows use the true AWG area; Tycab’s slightly lighter battery cable gives runs up to about 8% shorter at 8 B&S and 0 B&S. “Too small” means the current is at or above the cable’s rating, or leaves no margin for heat (for example 3mm cable rated at 20 A carrying 20 A, 5mm rated at 37 A carrying 30 A in a warm engine bay, or 6 B&S rated at 103 A carrying 100 A). “–” means the cable is far bigger than needed.

    What you’ll need

    • twin core auto cable (size from the table)
    • heavy duty single core auto cable (for high-current runs)
    • cable lugs and crimp terminals
    • inline fuse holder / circuit breaker / MIDI fuse holder
    • split loom tube and firewall grommet

    When to call an auto electrician

    • The run is long and the current is high (DC-DC chargers, inverters, winches, caravan charging).
    • You’re not sure what the accessory draws, or it has high start-up current (compressors, fridges, inverters).
    • Cable or terminals are getting hot, or accessories cut out under load.

    Need an auto electrician? Find local auto electricians and mobile services in your city.

    Find an auto electrician near you

    Related questions

    Q: Is “6mm” cable 6 mm²? A: No. In Australian auto cable, “6mm” usually describes the outside diameter including insulation. The copper area is about 4.6 mm². Always compare mm².

    Q: Why does my fridge cut out when I’m driving or camping? A: Often because the cable is too thin for the length, so the voltage at the fridge drops below its cut-out setting. Thicker cable or a shorter run usually fixes it.

    Q: Can I use thicker cable than I need? A: Yes. Thicker cable has less voltage drop and runs cooler. It costs more and is harder to route, but there’s no electrical downside.

    Q: Does the negative cable need to be as thick as the positive? A: Yes, if it carries the same current back to the battery. The voltage drop happens on both sides of the circuit.

    Sources

    1. Solar4RVs, “Understanding cable size types: mm, mm², B&S, AWG” – auto cable “mm” is outside diameter; 3mm/4mm/6mm copper areas; B&S to mm² conversions; heat derating note (AS/NZS 3008). https://www.solar4rvs.com.au/buying/buyer-guides/understanding-cable-size-types-mm-mm2-b_s-awg/ (checked October 2026)
    2. Tycab, automotive cable catalogue – single-core auto cable (ASC) and battery cable (ABC) stranding, mm², current ratings at 30°C and temperature derating factors. https://www.tyree.nz/wp-content/uploads/2019/09/Automotive-Comp.pdf (checked October 2026)
    3. HS Auto Parts, “Tycab cable – how to select the right gauge” – Tycab battery cable B&S sizes, mm² and rating guide. https://hsautoparts.com.au/tycab-cable-selection-guide/ (checked October 2026)
    4. Technical review, Ozautoelectrics (October 2026) – compare cable by conductor cross-section in mm²; “3mm” auto cable is 1.13 mm².
    5. Resistivity of copper (about 1.72 × 10⁻⁸ ohm-metre at 20°C), standard physical constant used to calculate the voltage-drop table.

  • How do I jump start a car safely?

    Quick answer

    Connect red to the flat battery’s positive, red to the good battery’s positive, black to the good battery’s negative, and the last black clamp to bare metal on the flat car’s engine or body, away from the battery. Start the good car, wait a few minutes, then start the flat car. Remove the leads in the reverse order. Check your owner’s manual first: some cars have dedicated jump points, and some hybrids and EVs have specific rules.

    Is this a DIY job?

    • Difficulty: Easy
    • Time: 10 to 20 minutes
    • Tools: jumper leads (heavy duty) or a portable jump starter, safety glasses, gloves, owner’s manuals for both cars
    • Skills: following a sequence carefully

    Jump starting is a normal roadside job, but getting the order wrong can cause sparks, damage electronics or, rarely, make a battery explode. Take your time.

    Step by step

    Jump start lead connection order Step 1: red clamp to the flat battery positive. Step 2: other red clamp to the good battery positive. Step 3: black clamp to the good battery negative. Step 4: last black clamp to bare metal on the flat car’s engine or body, away from the battery. Remove in reverse order. Jump starting: connect in this order Car with the flat battery + − Flat battery Engine Bare metal bolt, away from battery Car with the good battery + − Good battery 1 2 3 4 1 Red to flat + 2 Red to good + 3 Black to good − 4 Black to bare metal on flat car Remove in reverse: 4, 3, 2, 1. Check your owner’s manual for jump points, especially on hybrids, EVs and cars with the battery in the boot.
    Jump start lead connection order
    1. Check the manuals. Find the jump points for both cars. Some cars have remote jump terminals under the bonnet because the battery is in the boot or under a seat. Check whether either car is a hybrid or EV and what the manual allows.
    2. Check the batteries. Don’t jump start if either battery is cracked, leaking, swollen or badly corroded. Both systems must be the same voltage (almost all cars are 12V).
    3. Position the cars. Bring the good car close enough for the leads to reach, without the cars touching. Handbrakes on, automatics in Park, manuals in neutral. Both ignitions fully off, and switch off lights, radio and A/C.
    4. Protect yourself. Safety glasses and gloves on, rings and metal watch bands off. No smoking or flames. Keep leads away from fans and belts.
    5. Connect red to the flat battery’s positive (+).
    6. Connect the other red clamp to the good battery’s positive (+).
    7. Connect black to the good battery’s negative (−).
    8. Connect the last black clamp to bare metal on the flat car, such as an unpainted bolt or bracket on the engine, well away from the battery and moving parts. Don’t connect it to the flat battery’s negative post: the final connection can spark, and batteries can give off hydrogen gas.
    9. Start the good car and let it run for a few minutes.
    10. Start the flat car. Crank for no more than about 5 seconds at a time. If it doesn’t start, wait a couple of minutes before trying again. If it still won’t start after a few tries, the problem may not be the battery. (see Is it my starter motor or my battery?)
    11. Remove the leads in reverse order: black from the flat car’s earth point, black from the good battery, red from the good battery, red from the flat battery. Don’t let the clamps touch each other or any metal.
    12. Keep the jumped car running for a while, then have the battery charged properly and tested. Driving alone often won’t fully recharge a flat battery, and a battery that went flat for no clear reason may be failing or have a drain. (see Why does my car battery keep going flat?)

    Using a portable jump starter

    Follow the pack’s instructions. Most connect red to positive and black to an earth point or the negative post, with built-in reverse-polarity protection. Keep packs charged and stored out of direct sun, and avoid leaving lithium packs in a hot parked car. Don’t use a pack that is swollen, damaged or overheating.

    Specs table

    Connection order

    Step Clamp Connect to
    1 Red Flat battery positive (+)
    2 Red Good battery positive (+)
    3 Black Good battery negative (−)
    4 Black Bare metal earth point on the flat car, away from the battery

    Removal order: 4, 3, 2, 1 (the reverse).

    What you’ll need

    • jumper leads heavy duty or portable jump starter
    • safety glasses
    • smart battery charger (to recharge the battery properly afterwards)

    When to call an auto electrician

    • Either battery is damaged, leaking, swollen or smells of rotten eggs.
    • The car won’t start even with a good jump.
    • The car needs jump starting regularly.
    • Warning lights stay on after the car starts.
    • You’re not sure where to connect on a hybrid, EV or car with a battery in the boot. Never connect to or touch high-voltage parts or orange cables. Don’t use a hybrid or EV as the donor car unless its manual says that’s allowed.
    • If you’re not confident, call your roadside assistance provider.

    Need an auto electrician? Find local auto electricians and mobile services in your city.

    Find an auto electrician near you

    Related questions

    Q: Why not connect the last clamp to the flat battery’s negative post? A: The last connection often makes a small spark. Batteries can give off hydrogen gas, so the spark should happen away from the battery, on bare metal on the engine or body.

    Q: How long should I leave the car running after a jump start? A: Long enough to be sure it keeps running, then have the battery charged with a proper charger and tested. A short drive won’t fully recharge a flat battery.

    Q: Can I jump start a hybrid? A: Usually, yes, using the 12V jump points shown in the manual. The 12V battery powers up the system; you’re not jump starting the high-voltage battery. Follow the manual exactly.

    Q: Can jump starting damage my car? A: Done correctly, it rarely does. Reverse polarity, clamps touching, or connecting with ignitions on can damage electronics. Some vehicle manuals give specific warnings, so check yours.

    Sources

    1. RACV, “Car battery guide: how they work, when to replace them, and how to jump-start” – connection order; last clamp on unpainted metal on the flat car, not the flat battery’s negative; remove in reverse order. https://www.racv.com.au/royalauto/transport/cars/car-battery-guide-how-to-know-if-it-needs-replacing.html (checked October 2026)
    2. RAC (UK), “How to jump start a car in 10 steps” – crank limits, damaged battery warnings, hybrid donor caution. https://www.rac.co.uk/drive/advice/car-maintenance/how-to-jump-start-a-car/ (checked October 2026)
    3. ACCC Product Safety Australia, “Lithium-ion batteries guide” – store out of direct sunlight, not in hot places such as parked vehicles; don’t use swollen or damaged batteries. https://www.productsafety.gov.au/consumers/be-safe-around-the-home/safely-use-batteries-and-technology/lithium-ion-batteries-guide (checked October 2026)

  • How do I replace a brake light globe?

    Quick answer

    Get someone to press the brake pedal so you can see which light is out, then open the rear lamp access panel in the boot (or remove the tail light unit, as your owner’s manual describes), twist out the globe holder and swap the globe for one of the same type, often a P21/5W or P21W bayonet or a wedge-type globe. If both brake lights and the high third brake light are out together, the problem is more likely the fuse or brake light switch than the globes.

    Is this a DIY job?

    • Difficulty: Easy
    • Time: 10 to 30 minutes
    • Tools: owner’s manual, screwdriver or trim tool (some cars), clean cloth
    • Skills: none beyond care with plastic clips

    On most cars this is a simple job from inside the boot or tailgate. Some cars need the tail light unit unbolted and pulled out, which is still a DIY job if you’re patient with the clips.

    Step by step

    Common bayonet globe bases: BA15s, BAY15d and BAU15s Three 15 mm bayonet globes. BA15s (for example P21W): two locating pins opposite each other at the same height and one contact on the bottom. BAY15d (for example P21/5W): pins at different heights and two contacts on the bottom, so it only fits one way. BAU15s (for example amber PY21W): pins at the same height but not opposite each other, and one contact. Bayonet globe bases: how to tell them apart Side view (top row) and looking at the bottom of the base (bottom row). Not to scale. BA15s Pins level, opposite BAY15d Pins at different heights BAU15s Pins level, not opposite One contact Two contacts One contact, offset pin e.g. P21W (brake, reverse) e.g. P21/5W (brake + tail) e.g. PY21W (amber indicator) Always confirm the globe code in your owner’s manual or on the old globe before buying.
    Common bayonet globe bases: BA15s, BAY15d and BAU15s
    1. Find out which light is out. Have a helper press the brake pedal while you look at both brake lights and the high-mounted third brake light. No helper? Reverse up close to a garage door or shop window at night and use your mirrors.
    2. Check the pattern. If only one brake light is out, it’s almost certainly the globe. If all brake lights are out, check the fuse and the brake light switch at the pedal before buying globes.
    3. Find the globe type. The owner’s manual lists it. Common types are P21/5W (brake and tail in one globe), P21W (brake only) and W21/5W (wedge type, brake and tail). Buy a pair.
    4. Switch everything off. Ignition off, lights off.
    5. Get to the back of the lamp. Open the boot and look for a small access cover or panel behind the tail light. Some cars instead need two or three nuts or screws undone so the whole tail light unit can be eased out. Protect the paint with a cloth.
    6. Remove the globe holder. Most holders twist anticlockwise about a quarter turn and pull out. Some are a carrier plate with several globes, released by plastic tabs.
    7. Remove the old globe. Bayonet globes: push in gently, twist anticlockwise and pull out. Wedge globes: pull straight out.
    8. Check the old globe and holder. A blackened glass or broken filament confirms the globe has failed. Look for corrosion or melted plastic in the holder. Green corrosion can be cleaned off with a small brush and contact cleaner.
    9. Fit the new globe. A P21/5W globe has offset pins so it only fits one way. Don’t force it: if it won’t go in, turn it 180 degrees. Getting it in the wrong way round isn’t possible with a correct globe, but forcing it can damage the holder.
    10. Refit the holder and test. Check the brake light, tail light and indicator on that side before you refit any covers. Then refit the unit or cover and make sure any seals sit properly so water stays out.

    Specs table

    Common rear lamp globe types (12V)

    Type Filaments Wattage Base Typical use Notes
    P21/5W 2 21/5 W BAY15d (offset pins, two contacts) Brake and tail in one globe Often sold as “1157-type”
    P21W 1 21 W BA15s (level pins, one contact) Brake only, reverse, rear fog Often sold as “1156-type”
    W21/5W 2 21/5 W W3x16q (wedge) Brake and tail in one globe US equivalent 7443
    W21W 1 21 W W3x16d (wedge) Brake only, reverse US equivalent 7440

    US 1156 and 1157 globes fit the same bases as P21W and P21/5W but aren’t identical in rating. Buy by the code in your owner’s manual where you can.

    What you’ll need

    • P21/5W globe or P21W globe or W21/5W wedge globe (whichever your manual specifies)
    • electrical contact cleaner (if the holder is corroded)
    • Spare blade fuses (if all brake lights are out)

    When to call an auto electrician

    • All the brake lights are out and the fuse is fine. The brake light switch or wiring is the likely cause, and on many cars the switch also feeds cruise control, stop-start and the engine computer.
    • The brake lights stay on all the time. That can flatten the battery and confuses drivers behind you.
    • The high-mounted third brake light has failed. On many cars it’s a sealed LED unit that’s replaced as a whole.
    • The car’s tail lights are LED units. Most can’t be repaired by changing a globe.
    • A “lamp failure” warning stays on after the change, or the new globe works dimly or flickers.
    • The holder is melted or the wiring is burnt.

    Need an auto electrician? Find local auto electricians and mobile services in your city.

    Find an auto electrician near you

    Related questions

    Q: Is it illegal to drive with a brake light out? A: Brake lights are a required safety item. In Queensland, for example, a vehicle with a part that doesn’t work as intended counts as defective, and driving it can lead to a defect notice or fine. Check your own state’s rules. More importantly, the driver behind may not see you slow down. Replace it straight away.

    Q: Why do both my brake light and tail light share a globe? A: A P21/5W or W21/5W globe has two filaments: a dim one for the tail light and a bright one for braking. One globe does both jobs.

    Q: My new globe glows when I turn the headlights on and the indicator flashes oddly. Why? A: This often means a poor earth in the lamp unit or holder. Clean the earth connection and check the holder for corrosion.

    Q: Can I fit LED globes in my brake lights? A: Some LED replacements are available, but they can cause lamp-failure warnings on CAN-bus vehicles, and their light pattern in a reflector designed for a filament globe may not be as bright. The lamp must still meet the Australian Design Rules.

    Sources

    1. Wikipedia, “List of automotive light bulb types” – P21W, P21/5W, W21W and W21/5W bases, wattages and ANSI equivalents (7440, 7443). https://en.wikipedia.org/wiki/List_of_automotive_light_bulb_types (checked October 2026)
    2. Narva, “12V 21W P21W BA15S incandescent globe” (part 47382) – P21W is 12V 21W on a BA15s base. https://www.narva.com.au/products/47382 (checked October 2026)
    3. Narva, “12V 21/5W BAY15d globe” (part 17916BL) – 21/5W dual-filament on a BAY15d offset-pin base for stop/tail. https://www.narva.com.au/products/17916BL (checked October 2026)
    4. Queensland Government, Transport Operations (Road Use Management—Vehicle Standards and Safety) Regulation 2021, ss 7–9 – a vehicle is defective if a component doesn’t perform its intended function; offence to drive a defective vehicle; defect notices. https://www.legislation.qld.gov.au/view/whole/html/inforce/2026-07-01/sl-2021-0114 (checked October 2026)

  • How much do auto electricians charge in Australia?

    Quick answer

    Published Australian cost guides checked in October 2026 put auto electrician labour at roughly $90 to $180 an hour, with metro rates generally higher than regional ones. Common jobs range from a couple of hundred dollars for a battery supplied and fitted, to anywhere from a few hundred to over $1,000 for an alternator or starter motor. Prices vary a lot by location, vehicle and fault, so get a written quote for your car.

    Is this a DIY job?

    • Difficulty: Not applicable (this is a cost guide)
    • Time: 10 minutes to gather the details for a quote
    • Tools: your car’s make, model, year and VIN; photos of any warning lights
    • Skills: none

    Some jobs in this guide, like swapping a battery or a globe, are easy to do yourself. Others, like diagnosing an intermittent fault or fitting a brake controller, are better left to a professional. Each master article in this library has an “Is this a DIY job?” section to help you decide.

    What affects the price

    1. Location. Metro rates are generally higher than regional rates, though regional jobs can add travel.
    2. Mobile or workshop. Mobile services save you a tow or a trip, and may charge a call-out fee. A workshop may have better equipment for complex faults.
    3. The vehicle. European, luxury, hybrid and EV models often take longer and need specialist tools or software. Parts can cost more.
    4. Parts. New, reconditioned or genuine parts all cost differently. Ask which is being quoted.
    5. Diagnosis time. A simple fault may take minutes to find. An intermittent fault or a drain that only appears overnight can take hours.
    6. Access. A battery under the bonnet is quick. An alternator or starter buried under other parts takes much longer.
    7. When you need it. After-hours, weekend and emergency call-outs usually cost more.

    Step by step: getting an accurate price

    1. Describe the problem clearly. What happens, when it started, whether it’s constant or comes and goes, and any warning lights or noises.
    2. Give your vehicle details. Make, model, year, engine and VIN. Mention modifications (dual battery, lights, towbar wiring).
    3. Send photos. A photo of the dash with the warning light on, and of any visible damage, helps.
    4. Ask how they charge. Is it a fixed price, an hourly rate, or a diagnostic fee first? Is there a call-out fee? Does the price include GST?
    5. Ask about parts. New or reconditioned? What warranty comes with the parts and the labour?
    6. Get it in writing. Ask for a written quote or estimate, and ask to be contacted before any extra work is done.
    7. Compare like with like. A cheaper quote may use different parts or exclude diagnosis. Check what’s included before you compare.

    Specs table

    Published price ranges (checked October 2026)

    These figures come from published Australian cost guides and quote platforms, not from a formal industry survey. They’re a starting point for budgeting, not a quote. Unless noted, prices include parts and labour.

    Item Price range found Source and date
    Hourly labour, general $90 to $150 per hour ServiceTasker cost guide, updated February 2026
    Hourly labour, South Australia About $110 to $180 per hour The Quote Yard, June 2026
    Hourly labour, mobile auto electricians (average) About $128 per hour ServiceSeeking, May 2026
    Hourly labour, metro vs regional $120 to $150 metro; $90 to $120 regional ServiceTasker, updated February 2026
    Standard call-out fee (urban) $50 to $100 ServiceTasker, updated February 2026 (one source)
    After-hours or emergency work $130 to $250 per hour ServiceTasker, updated February 2026 (one source)
    Electrical diagnostic or scan $90 to $250 The Quote Yard (SA), June 2026
    Battery: standard battery only $120 to $180 Yellow Pages, updated May 2026
    Battery: premium (e.g. AGM) battery only $185 to $450 Yellow Pages, updated May 2026
    Battery supplied and fitted, standard $150 to $400 ServiceTasker, updated February 2026
    Alternator replacement $200 to $500 ServiceTasker, updated February 2026
    Alternator or starter motor replacement $400 to $1,500 The Quote Yard (SA), June 2026
    Wiring or fault repair $150 to $900 The Quote Yard (SA), June 2026
    Air conditioning regas or repair $150 to $1,500 The Quote Yard (SA), June 2026
    Accessory fit-out (dual battery, lights) $300 to $2,500 The Quote Yard (SA), June 2026
    Hybrid or EV high-voltage diagnostic $150 to $600 The Quote Yard (SA), June 2026

    Real fixed-price examples (Melbourne, July to October 2026)

    Listed fixed quotes on a booking platform, including GST, for specific vehicles. They show how much prices vary with the vehicle.

    Job Vehicle Listed price
    Alternator replacement (plus belt and extras) 2010 Toyota RAV4 $602
    Alternator replacement (plus extras) 2006 Mercedes-Benz Sprinter $789
    Starter motor replacement (plus extras) 2007 Mazda 3 $397
    Starter motor replacement 2007 Mercedes-Benz B-Class $967
    “Vehicle will not start” inspection Two vehicles $99 and $188

    Why the alternator ranges differ: the lower figures may not include all parts, or may reflect a simple car with easy access. The higher figures cover harder-to-reach units, newer or European vehicles, and new rather than reconditioned parts.

    What you’ll need

    Nothing to buy for a quote. If you decide to do a simple job yourself, the parts are listed in each master article, for example:

    • car battery
    • OBD2 code reader
    • digital multimeter

    When to call an auto electrician

    • You have a warning light, no-start or electrical fault you can’t trace with simple checks.
    • The job involves airbags/SRS, hybrid or EV high-voltage systems, or air conditioning refrigerant. These are professional-only. Refrigerant work must be done by someone holding a refrigerant handling licence from the Australian Refrigeration Council (ARCtick).
    • You’re adding accessories that draw high current: dual batteries, inverters, brake controllers, winches.
    • Your car is under warranty and you want the work documented. According to the ACCC (as reported by CHOICE), you don’t have to use the dealer to keep the manufacturer’s warranty, as long as the work is done by qualified people to the manufacturer’s specifications with suitable parts. Keep your invoices. Some extended warranties have their own conditions.

    Need an auto electrician? Find local auto electricians and mobile services in your city.

    Find an auto electrician near you

    Related questions

    Q: Do auto electricians charge for diagnosis? A: Many do, either as a fixed diagnostic fee or by the hour. Finding a fault takes time and equipment. Ask up front how diagnosis is charged and whether it comes off the repair bill if you go ahead.

    Q: Is a mobile auto electrician more expensive? A: Not always. Some charge a call-out fee, but you save on towing and time. For complex faults, a workshop with more equipment can sometimes be quicker overall.

    Q: Can I get a quote over the phone? A: For simple jobs like a battery or a known part, often yes. For faults, a firm price usually needs a diagnosis first, because the same symptom can have several causes. (see Can I get a quote for an auto electrical problem?)

    Q: Do auto electrician prices include GST? A: It depends on the business. Always ask whether a quote includes GST so you can compare quotes fairly.

    Q: How can I keep the cost down? A: Describe the fault clearly, note when it happens, and take photos of warning lights. Keep the battery healthy and terminals clean, and fix small problems before they turn into bigger ones.

    Sources

    1. ServiceTasker, “How much do auto electricians charge per hour? Cost guide 2026” – hourly, call-out, after-hours, battery and alternator ranges. Updated February 2026. https://servicetasker.com.au/cost-guides/how-much-do-auto-electricians-charge-per-hour (checked October 2026)
    2. ServiceSeeking, “Mobile auto electrician prices in Australia 2026” – average hourly rate. Published May 2026. https://www.serviceseeking.com.au/pricing/mobile-auto-electrician-prices-in-australia-2026 (checked October 2026)
    3. The Quote Yard, “Auto electrician SA – typical costs” – SA labour rate and job ranges. Published June 2026. https://www.thequoteyard.com.au/services/auto-electrician-sa (checked October 2026)
    4. Yellow Pages, “How much does a car battery cost?” – battery price ranges and fitting cost. Updated May 2026. https://www.yellowpages.com.au/articles/mechanics-and-motor-engineers/price-of-car-battery-replacement (checked October 2026)
    5. AutoGuru, mobile auto electrician listings (Melbourne) – fixed-quote examples, July to October 2026. https://www.autoguru.com.au/auto-electrician/vic/melbourne/central-park/mobile (checked October 2026)
    6. Australian Refrigeration Council, “What type of licence do I need?” – automotive air conditioning work and refrigerant handling need an ARC refrigerant handling licence (automotive). https://www.arctick.org/licensing/licence-types/ (checked October 2026)
    7. CHOICE, “Car warranties and dealer servicing” – quotes the ACCC on servicing outside the dealer network. https://www.choice.com.au/transport/cars/servicing/articles/car-warranties-and-dealer-servicing (checked October 2026)

  • How do I replace an indicator globe?

    Quick answer

    If one side’s indicator suddenly flashes fast, a globe on that side has usually blown. Find the globe type in your owner’s manual (often PY21W, P21W or WY5W), reach the globe holder from behind the lamp, twist it out, fit the new globe and test before you put everything back. Front indicators on some modern cars are reached through the wheel arch or need the headlight removed.

    Is this a DIY job?

    • Difficulty: Easy (rear and side indicators); Easy to Pro (front, depending on the car)
    • Time: 10 to 30 minutes
    • Tools: owner’s manual, screwdriver or trim tool, torch
    • Skills: gentle handling of plastic clips

    Rear indicators are usually reached from the boot, the same way as the brake lights. Side repeaters on the guards often pop out with a gentle push and twist. Front indicators vary the most: some twist out from behind the headlight, some are reached through an opening in the wheel arch liner, and some need the bumper or headlight removed.

    Step by step

    Common bayonet globe bases: BA15s, BAY15d and BAU15s Three 15 mm bayonet globes. BA15s (for example P21W): two locating pins opposite each other at the same height and one contact on the bottom. BAY15d (for example P21/5W): pins at different heights and two contacts on the bottom, so it only fits one way. BAU15s (for example amber PY21W): pins at the same height but not opposite each other, and one contact. Bayonet globe bases: how to tell them apart Side view (top row) and looking at the bottom of the base (bottom row). Not to scale. BA15s Pins level, opposite BAY15d Pins at different heights BAU15s Pins level, not opposite One contact Two contacts One contact, offset pin e.g. P21W (brake, reverse) e.g. P21/5W (brake + tail) e.g. PY21W (amber indicator) Always confirm the globe code in your owner’s manual or on the old globe before buying.
    Common bayonet globe bases: BA15s, BAY15d and BAU15s
    1. Work out which globe is out. Switch on the hazard lights and walk around the car. Check front, rear and side repeaters. A blown globe usually makes the dash indicator light and the ticking flash about twice as fast on that side.
    2. Find the globe type. Check the owner’s manual. Indicators commonly use PY21W (amber glass, bayonet), P21W (clear glass, for amber lenses), or small WY5W wedge globes in side repeaters. Buy a pair.
    3. Switch off. Ignition and lights off.
    4. Rear indicator: open the boot, remove the access cover or tail light unit as your manual shows, then twist the indicator holder out (usually anticlockwise).
    5. Side repeater: many slide or push one way to release a clip, then tilt out. Don’t lever against the paint; use a plastic trim tool and a cloth. Pull the holder out of the back and replace the wedge globe.
    6. Front indicator: look behind the headlight for a holder with an amber globe. If it isn’t reachable, check the manual. Some cars have an access flap in the wheel arch liner (turning the steering wheel gives more room). If the manual says to remove the bumper or headlight, consider a workshop.
    7. Remove the old globe. Bayonet: push in, twist anticlockwise, pull out. Wedge: pull straight out.
    8. Match the colour. If the lamp lens is clear, the globe must be amber (PY21W or WY5W). If the lens is amber, a clear globe (P21W or W5W) is normally used. An indicator must show amber light.
    9. Fit the new globe. PY21W globes have offset pins and only fit one way. Don’t force them.
    10. Test before refitting. Check the indicator flashes at the normal rate on both sides, then refit the holder, covers and lamp unit with seals in place.

    Specs table

    Common indicator globe types (12V)

    Type Glass Wattage Base Typical use
    PY21W Amber 21 W BAU15s (pins offset, one contact) Front and rear indicators behind clear lenses
    P21W Clear 21 W BA15s (pins level and opposite) Indicators behind amber lenses
    WY5W Amber 5 W Wedge (W2.1×9.5d) Side repeaters behind clear lenses
    W5W Clear 5 W Wedge (W2.1×9.5d) Side repeaters behind amber lenses

    Fitment varies by vehicle. Your owner’s manual or the old globe has the correct code.

    What you’ll need

    • PY21W amber indicator globe or P21W globe (front and rear, as specified)
    • WY5W amber wedge globe or W5W wedge globe (side repeaters)
    • plastic trim tool
    • If you’re converting to LED: LED flasher relay or load resistor (see related questions)

    When to call an auto electrician

    • The front indicator needs the bumper or headlight removed.
    • A new globe doesn’t fix the fast flashing, or no indicator on one side works at all. Check the fuse, then suspect the wiring, earth or switch.
    • The indicators don’t work at all, or the hazard lights work but the indicators don’t (or the reverse). That points to the flasher, switch or body control module.
    • Your car shows a “lamp failure” or bulb warning after the change, or you’ve fitted LED globes and get warnings. Many modern cars monitor lamp current through a CAN-bus control module, and the fix depends on the vehicle.
    • The indicator lamp is a sealed LED unit.

    Need an auto electrician? Find local auto electricians and mobile services in your city.

    Find an auto electrician near you

    Related questions

    Q: Why are my indicators flashing fast? A: Usually a globe has blown on that side. If you’ve fitted LED indicator globes, they draw so little current that the car thinks a globe is out. (see Why are my indicators flashing fast?)

    Q: Can I use a clear globe behind a clear indicator lens? A: No. The light from an indicator must be amber. Behind a clear lens you need an amber globe such as a PY21W or WY5W.

    Q: Why does my amber indicator globe look pale or flash white? A: The amber coating on cheaper globes can fade over time. Replace faded globes, because the light must still be amber.

    Q: Do I need to replace indicator globes in pairs? A: It isn’t essential, but the other side has done the same hours and often fails soon after. Replacing both keeps the colour matched.

    Sources

    1. OSRAM, PY21W product data – BAU15s base, 12 V, 21 W. https://osram.com/ecat/Lamps%20with%20metal%20bases-Signal%20lamps-Car%20lighting-Automotive/ae/en/GPS01_1057060/ZMP_60924 (checked October 2026)
    2. OSRAM, P21W product data – BA15s base, 12 V, 21 W. https://osram.com/ecat/Lamps%20with%20metal%20bases-Signal%20lamps-Car%20lighting-Automotive/gb/en/GPS01_1057060/ZMP_1285824 (checked October 2026)
    3. OSRAM, WY5W product data – W2.1×9.5d wedge base, 12 V, 5 W. https://www.osram.co.uk/ecat/gb/en/GPS01_1057061/ZMP_4057277 (checked October 2026)
    4. Federal Register of Legislation, Vehicle Standard (Australian Design Rule 13/00 – Installation of Lighting and Light Signalling Devices on other than L-Group Vehicles) 2005 – Table 1 lists direction-indicator lamps as amber. https://www.legislation.gov.au/F2005L03991/latest (checked October 2026)
    5. Federal Register of Legislation, Vehicle Standard (Australian Design Rule 6/00 – Direction Indicators) 2005 – component rule for direction indicators. https://www.legislation.gov.au/F2005L03907/latest (checked October 2026)

  • How do I check and replace a blown fuse?

    Quick answer

    Switch the ignition off, find the right fuse using the chart in your owner’s manual or on the fuse box lid, pull it out with the fuse puller, and look through the plastic: a broken metal strip means it’s blown. Replace it with a fuse of exactly the same rating (the number on top and the colour). If the new fuse blows again, there’s a fault in that circuit that needs finding: never fit a bigger fuse.

    Is this a DIY job?

    • Difficulty: Easy
    • Time: 5 to 15 minutes
    • Tools: owner’s manual, fuse puller (often clipped inside the fuse box), torch, test light or multimeter (optional)
    • Skills: none

    Checking and replacing a blade fuse is one of the simplest car jobs. Finding why a fuse keeps blowing is harder and may need an auto electrician.

    Step by step

    Blade fuse colour chart and how to spot a blown fuse Left: a good blade fuse with an unbroken metal strip, and a blown fuse with a broken strip. Right: standard blade fuse colours by rating: 1 A black, 2 A grey, 3 A violet, 4 A pink, 5 A tan, 7.5 A brown, 10 A red, 15 A blue, 20 A yellow, 25 A clear, 30 A green, 40 A orange. Maxi fuses use a different colour code. Blade fuses: good or blown, and the colour code 10 Good Unbroken strip 10 Blown Gap or blackened strip Replace with the same rating Never fit a higher-rated fuse. If it blows again, there’s a fault in that circuit. Regular, mini and micro blade fuses 1 A Black 2 A Grey 3 A Violet 4 A Pink 5 A Tan 7.5 A Brown 10 A Red 15 A Blue 20 A Yellow 25 A Clear 30 A Green 40 A Orange Maxi fuses use a different colour code For example 50 A maxi = red, 60 A maxi = blue. Always read the number printed on the fuse.
    Blade fuse colour and rating chart, and how to spot a blown fuse
    1. Switch off. Ignition off, key out, and switch off the item that stopped working.
    2. Find the fuse boxes. Most cars have at least two: one under the bonnet and one inside the cabin (under the dash, in the side of the dash, or behind a panel in the footwell or glovebox). Some have more, including one in the boot. Your owner’s manual shows where.
    3. Find the right fuse. Use the chart in the manual or on the inside of the fuse box lid. Fuses are labelled by position, rating and the circuit they protect (for example “CIG”, “RADIO”, “P/W”).
    4. Pull the fuse out. Use the plastic fuse puller, or fine-nose pliers, gripping the plastic body. Pull straight out.
    5. Check it. Hold it up to the light. A good fuse has an unbroken metal strip between the two blades. A blown fuse has a gap or a melted, blackened strip. If you can’t tell, test it: with a multimeter on continuity or resistance, a good fuse reads close to zero ohms. Many blade fuses also have small test points on top, so you can test them in place with a test light (ignition on for circuits that are only live with the ignition).
    6. Fit an identical replacement. Same type (micro, mini, standard or maxi), same rating (number on top), same colour. Push it fully into the slot.
    7. Test the circuit. Switch on and check the item works.
    8. If it blows again straight away, stop replacing fuses. There’s a short circuit or an overload in that circuit.
    9. Replace your spare. Many fuse boxes have spare fuses clipped inside. Replace any you use.

    Checking a relay

    Relays are the larger plug-in cubes in the fuse box. They switch high-current items like headlights, horns, fans and fuel pumps. A simple check: with the ignition off, swap the suspect relay with an identical relay (same part number) from a circuit you can test, such as the horn. If the fault moves with the relay, the relay is faulty. If you’re not sure two relays are identical, don’t swap them. (see How do I wire a 12V relay (pins 30, 85, 86, 87)?)

    Specs table

    Standard blade fuse colours (regular, mini and micro blade fuses)

    Rating Colour
    1 A Black
    2 A Grey
    3 A Violet
    4 A Pink
    5 A Tan
    7.5 A Brown
    10 A Red
    15 A Blue
    20 A Yellow
    25 A Clear (natural)
    30 A Green
    40 A Orange

    Not every rating is made in every size, but where a rating exists the colour is the same.

    Maxi fuses use a different colour code. For example, a 50 A maxi fuse is red and a 60 A maxi is blue. Always go by the number printed on the fuse, not just the colour.

    Fuse types by size

    Type Typical use
    Micro2 / Micro3 Many newer vehicles
    Mini blade Most cars from the 1990s on
    Standard (ATO/ATC) blade Older cars, many accessories and trailers
    Maxi blade High-current circuits under the bonnet
    Bolt-in or cartridge fuses Main supply and high-current circuits (leave to a professional)

    What you’ll need

    • mini blade fuse kit / standard blade fuse kit / micro blade fuses (whichever your car uses)
    • fuse puller
    • 12V test light or digital multimeter
    • automotive relay (if a relay has failed; match the part number)

    When to call an auto electrician

    • A fuse blows again after replacement. There’s a short or overload to find.
    • The blown fuse protects the airbags/SRS, ABS, engine management or a module. Don’t keep replacing these: get the fault diagnosed.
    • A large bolt-in, cartridge or main fuse has blown. These protect major circuits and often point to a serious fault.
    • Fuses, relays or the fuse box show signs of melting or heat damage.
    • It’s a hybrid or EV and the fault involves the high-voltage system. Never touch orange cables or high-voltage fuses.

    Need an auto electrician? Find local auto electricians and mobile services in your city.

    Find an auto electrician near you

    Related questions

    Q: Can I use a higher-rated fuse if I don’t have the right one? A: No. The fuse protects the wiring. A higher-rated fuse can let the wiring overheat and start a fire before the fuse blows. Never replace a fuse with wire, foil or any other metal object, even to get home.

    Q: Can I use a fuse from another circuit temporarily? A: Only if it’s exactly the same rating and from a circuit you don’t need, such as the cigarette lighter. Replace it with the correct fuse as soon as you can, and never borrow from safety systems.

    Q: Why does my fuse look fine but the circuit doesn’t work? A: Fuses can crack internally where you can’t see it, so test it with a multimeter or test light. If the fuse is fine, check the relay, switch, wiring and the item itself.

    Q: Where’s my car’s fuse box? A: Most cars have one under the bonnet and one in the cabin, and some have one in the boot. The owner’s manual shows the locations and what each fuse does.

    Sources

    1. Littelfuse, ATO and MAXI blade fuse datasheet (via Farnell) – blade fuse colour codes by rating; maxi colour code differs. https://www.farnell.com/datasheets/82316.pdf (checked October 2026)
    2. ISO 8820-3 – Road vehicles, fuse-links, Part 3: fuse-links with tabs (blade type). Referenced as the standard behind the colour code; not quoted.
    3. Volvo Cars Australia, “Replacing a fuse” (V90 owner information) – replace with the same colour and amperage; a higher-rated fuse or a foreign object can damage the electrical system and cause a fire. https://www.volvocars.com/au/support/car/v90/article/97f7da007063b1e3c0a8015164d3df7a/ (checked October 2026)
    4. Kia owner’s manual, “Fuse replacement” – same rating only; a fuse that blows again means an electrical problem; never use wire or foil in place of a fuse. https://ownersmanual.kia.com/full_webhelp/KA4/2024/en_US/topics/t00732.html (checked October 2026)