Quick answer
Fast flashing (often called hyperflash) almost always means the car thinks an indicator globe on that side has failed. Usually a globe really has blown, but it also happens after fitting LED globes, because they draw so little current the system reads them as blown. Replace the blown globe; or, for LEDs, fit a flasher relay made for LEDs, add load resistors, or have the body control module recoded, keeping in mind that aftermarket LED replacement globes may not keep the lamp ADR compliant.
Is this a DIY job?
- Difficulty: Easy (globe replacement); Medium (load resistors or a flasher relay)
- Time: 10 minutes to find the cause; 15 minutes to 1 hour to fix
- Tools: owner’s manual, screwdriver or trim tool, torch, multimeter for wiring checks
- Skills: replacing a globe; basic wiring for resistors
Finding and replacing a blown globe is a simple DIY job. If the car uses a body control module to run the indicators, or the fix involves coding, it’s a job for an auto electrician with the right scan tool.
Why it happens
Australian vehicles must have indicators that flash between 60 and 120 times a minute (90 ± 30). If one globe fails, the design rules require the others to keep flashing, and the driver’s tell-tale must show there’s a problem: by going out, staying on steady, or changing rate. Many vehicles do it by flashing fast.
On older cars, the flasher unit senses the current drawn by the globes. Lose one globe’s worth of current and the flasher speeds up. On newer cars, the body control module measures the current in each indicator circuit and does the same job. Either way, an LED globe that draws a fraction of the current of a 21 W globe looks like a blown globe.
Step by step
- Switch on the hazard lights. Walk around the vehicle and check every indicator: front, rear, side repeaters, and any trailer lights if one is connected.
- Note which side flashes fast. Usually it’s only one side. That points to a globe, globe holder or wiring fault on that side.
- Replace any globe that’s out. Use the type listed in the owner’s manual, and match amber to amber. (see How do I replace an indicator globe?)
- If every globe lights, look closer. A globe that glows dimly, a corroded globe holder, or a poor earth on that side can reduce the current and cause fast flashing. Clean the holder and check the earth.
- Check for a trailer fault. If it only happens when the trailer is plugged in, the problem is usually a trailer globe, plug or earth. (see Why aren’t my trailer lights working?)
- If you’ve fitted LED indicator globes, that’s likely the cause. Choose one of the fixes below, or go back to the original filament globes.
- If both sides flash fast, or the rate changes at random, suspect the flasher relay or a body control module fault, especially after other electrical work. Have it scanned.
Fixing fast flashing after fitting LED globes
Option 1: an LED flasher relay. On older vehicles with a plug-in flasher relay, swap it for an electronic flasher designed for LEDs. It flashes at the normal rate whatever the load. Match the pin layout and number of pins to your original flasher. Be aware it may also stop the indicators warning you when a globe really fails.
Option 2: load resistors. On many modern vehicles, load resistors are essential when fitting LED globes. These vehicles sense the current in the indicator circuit, and without the extra load they show an indicator warning, flash fast, or don’t work normally. A load resistor is wired across each LED globe, from the indicator wire to earth, so the circuit draws about the same current as the original globe. One resistor is needed for each globe replaced. Load resistors work by turning that extra current into heat: one 12V resistor designed to stand in for a 21 W globe is rated by its maker to reach up to 170°C. Mount every resistor on bare metal, away from plastic, carpet, paint and wiring, and never leave one loose in a lamp housing or behind trim. Note that once you’ve added resistors, much of the LED’s power saving is gone.
Option 3: coding the body control module. On many modern vehicles the indicators are run by the body control module, and there’s no flasher relay to change. Some vehicles can be recoded with a scan tool to accept LED globes; others can’t, and adding resistors may still trigger faults. This varies by make and model, so check with an auto electrician who has the right diagnostic equipment for your vehicle.
Option 4: go back to filament globes. If the vehicle came with filament globes, refitting the correct type is the simplest way to restore normal flashing and keep the lamp compliant.
Keep it legal. Factory indicator lamps are approved under the Australian Design Rules with the type of globe they were designed for. Aftermarket LED replacement globes have generally not been approved for road use in Australia, and the NT Government’s vehicle standards page warns that non-complying lighting can see a vehicle defected or refused registration. Whatever you fit, the indicator must still show amber light and flash at the normal rate. Australia made a new standard for LED light sources (ADR 101/00) in July 2026, based on the UN rule that also covers approved LED replacement globes. Until a replacement globe is clearly marked as approved for your lamp and accepted by your state’s road authority, the safe choice is the globe type the lamp was designed for.
Specs table
| Item | Figure | Notes |
|---|---|---|
| Legal indicator flash rate | 90 ± 30 flashes a minute (60 to 120) | Set by the lighting installation rules; the rate may change when a lamp fails |
| Common indicator globes | PY21W or P21W (21 W); WY5W or W5W (5 W) | Check the owner’s manual for your vehicle |
| Current drawn by a 21 W globe | about 1.75 A at 12 V | 21 W ÷ 12 V |
| Example 12V load resistor for a 21 W globe | 8 Ω, sold to stand in for a 21 W globe | One maker’s figure; draws about 1.5 A at 12 V (12 V ÷ 8 Ω) |
| Load resistor surface temperature | up to 170°C | Maker’s figure; mount on metal only |
Globe types and resistor values vary by vehicle. Use the globe code from your owner’s manual and a resistor matched to the wattage of the globe it replaces.
What you’ll need
- PY21W amber indicator globe or P21W globe (as specified)
- WY5W amber wedge globe (side repeaters, as specified)
- LED flasher relay (vehicles with a plug-in flasher)
- 12V LED load resistor 21W (one per LED globe)
- self-tapping screws for mounting resistors to metal
- crimp terminals and adhesive lined heat shrink
- digital multimeter
When to call an auto electrician
- A new globe doesn’t fix the fast flashing, or both sides flash fast.
- Your vehicle’s indicators are run by a body control module and need coding, or a lamp failure warning won’t clear.
- The indicator lamps are sealed LED units. These normally can’t be repaired by replacing a globe.
- You’ve fitted LED globes and want to be sure the vehicle stays roadworthy.
- You can smell hot plastic or see melting near a load resistor. Switch off and stop using the indicators until it’s checked.
Need an auto electrician? Find local auto electricians and mobile services in your city.
Related questions
Q: Why do my indicators flash fast on one side only? A: A globe on that side has usually blown, or it isn’t getting a good earth. Check every indicator on that side with the hazards on.
Q: Why do my indicators flash fast with LED globes? A: LEDs draw much less current than filament globes, so the flasher or body control module thinks a globe has blown. An LED flasher relay, load resistors or coding can fix it, but the lamp must stay compliant.
Q: Is fast flashing illegal? A: Indicators must flash between 60 and 120 times a minute in normal use. Fast flashing is a warning that something has failed, so fix the cause rather than live with it.
Q: Are LED globes legal in my indicators? A: Aftermarket LED replacement globes have generally not been ADR approved in Australia. Check with your state road authority before fitting them.
Q: Do load resistors get hot? A: Yes, very. They’re designed to turn electricity into heat and can reach well over 100°C, so they must be mounted on metal, away from plastics and wiring.
Sources
- UN Regulation No. 48 (installation of lighting and light-signalling devices), as published in the Official Journal of the EU – para 6.5.9: direction indicators flash 90 ± 30 times per minute; on failure of one lamp the others continue to flash, and the frequency may differ; para 6.5.8: tell-tale signals a malfunction by going out, staying on steady or changing frequency. https://eur-lex.europa.eu/eli/reg/2011/48(2)/oj/eng/pdf (checked October 2026)
- Department of Infrastructure, Vehicle Standard (Australian Design Rule – Vehicle Lighting) Amendment Instrument 2022 – ADR 13/00 installation requirements follow the UN Regulation 48 structure (clause 7.7 table, “6.5 Direction Indicator Lamp”); ADR 6/00 direction indicators reference UN Regulation No. 6. https://legislation.gov.au/F2023L00042/asmade/2023-01-19/text/original/epub/OEBPS/document_1/document_1.html (checked October 2026)
- Department of Infrastructure, Draft ADR 101/00 – Light Emitting Diode (LED) Light Sources (consultation draft, August 2025) – based on UN Regulation No. 128, including LED substitute light sources. https://www.infrastructure.gov.au/sites/default/files/documents/draft-adr-august-2025-101-00-vehicle-standard-australian-design-rule-101-00-light-emitting-diode-led-light-sources-2025_0.pdf (checked October 2026)
- Northern Territory Government, “Vehicle accessories” – aftermarket LED replacement globes marked off-road use only are not ADR compliant; vehicles with non-complying lighting may be defected or refused registration. https://nt.gov.au/driving/rego/vehicle-compliance-and-modification/vehicle-accessories (checked October 2026)
- Narva, “Why aren’t my indicators flashing correctly?” – load-sensitive flashers and LED globes; load resistor specification (12V, 21W, 8 Ω); operating temperatures up to 170°C; mount on heat-resistant metal. https://narva.com.au/narva-university/blogs/indicator-issues (checked October 2026)
- Narva, “Why aren’t aftermarket LED globes ADR approved?” – aftermarket LED replacement globes are not ADR approved; factory-fitted LEDs are. https://www.narva.com.au/blogs/blogs/2020/Dec/20/aftermarket-led-globes-adr-approval (checked October 2026)
- Wikipedia, “List of automotive light bulb types” – PY21W, P21W (21 W), WY5W, W5W (5 W). https://en.wikipedia.org/wiki/List_of_automotive_light_bulb_types (checked October 2026)
- Federal Register of Legislation, Vehicle Standard (Australian Design Rule 101/00 – Light Emitting Diode (LED) Light Sources) 2026, registered 9 July 2026. https://www.legislation.gov.au/F2026L00926/asmade/text (checked October 2026)