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My Turn Signal (Indicators) Flash Fast on One Side?

To get turn signals (indicators) to flash, there needs to be something in the electrical circuit that automatically switches the turn signal lights on and off when power is applied.

Front Turn Signal - Mini Cooper
Front Turn Signal – Mini Cooper

A turn signal relay (indicator relay or flasher relay) is used in older vehicles. In newer cars, the turn signals are controlled by electronics (usually one of the many circuits buried inside one of the vehicles control units).

It’s likely that a broken lamp will have caused the indicators to flash faster (hyper flashing). But there can be other reasons…

How to Fix Turn Signals Flashing Fast:

Fitted LED lights?

Why Would a Broken Bulb Cause my Indicators to Flash Faster (Hyper Flashing)?

A light bulb creates a load on the electrical circuit. When a lamp blows, there is less load on the electrical circuit. The smaller load causes the electronics (or turn signal relay) to switch on and off faster, thereby causing the turn signals to flash faster.

On Newer Vehicles:

Check the turn signals to see if any of the light bulbs have blown, and replace as necessary.

With most modern cars, the indicators are controlled by electronics. These electronics are normally incorporated within one of the control modules in the vehicle. If this is what’s fitted to your vehicle, the defect is more likely to be a defective lamp, as the electronics tend to be more reliable.

Turn Signal Electronics - The Footwell Control Module (Mini)
Turn Signal Electronics – Contained Within The Footwell Control Module (Mini)
On Older Vehicles:

As well as a blown light bulb causing the turn signals to flash faster, older vehicles were fitted with a turn signal relay (indicator relay or flasher unit).

These relays (or flasher units) can fail and will have similar symptoms to a blown light bulb. Or, they just fail completely! These relays were often controlled by a bimetallic strip, which would rapidly heat up and cool down (and are not as reliable as modern electronics).

Notes:
  • Only replace turn signal (indicator) light bulbs with the same type (see the section on LED’s below).
  • Check the replacement light bulb is the correct wattage, or the light will be too dim or too bright.
LED Light Bulb (12v BA15 21w)
LED Light Bulb (Equivalent to a 12v P21W BA15s)

Led light bulbs are now starting to replace the old filament light bulbs.

Unfortunately with turn signals (indicators), you cannot directly replace a filament light bulb with an LED replacement, without modifications.

Turn Signals – Why Can’t I Replace a Filament Light Bulb with an LED?

An LED light bulb places a different (smaller) load on the electrical circuit. Your turn signals will therefore flash faster with an LED light bulb fitted.

There are ways around this, but it involves fitting additional components. Unless you specifically want LED turn signals, it’s easier to replace the light bulbs with what was originally fitted to the vehicle.

How to Make LED Turn Signals Flash Correctly:

To upgrade turn signals to use LED’s, you will need to take account of the different load LED’s have on the electrical circuit, (compared to filament light bulbs).

To modify the vehicle to use LED’s (for turn signals), you have two main choices:

There are advantages and disadvantages to both:

Precautions:
  • Any installation is at your own risk. Each vehicle may be different, or may have been previously modified.
  • Disconnect the battery, when wiring vehicles.
  • If you’re unsure, use a qualified auto electrician. As modern vehicles electronics can be damaged easily.

Install an LED Compatible Turn Signal Relay:

Advantages:

You will only need one LED compatible turn signal relay for all the lights.

LED Turn Signal Relay
LED Turn Signal Relay

Dependant on what’s fitted to the vehicle…

If a turn signal relay is fitted, it could be a straight forward swap, as long as the pin configuration is the same.

Disadvantages:

If the turn signals are controlled by electronics within one of the vehicles control modules, the only way of adding the LED turn signal relay is to bypass the control module. I.e. Remove the turn signal inputs and outputs from the control module, and connect them directly to the LED turn signal relay.

This is potentially intrusive to the vehicles electronics, so great care should be taken.

Replacing a filament light bulb with an LED light bulb, can sometimes cause a vehicles electronics (the CanBus system) to think there is a bulb failure. If an ‘LED’ turn signal relay does not take account of this (by providing the correct additional load), you may still have to install load resistors to mimic a filament light bulb. Check with your supplier to ensure the ‘LED’ turn signal relay is the correct one for your vehicle?

Increase the load on the electrical circuit by introducing load resistors:

50W 6 ohm Load Resistor
50W 6 ohm Load Resistor

Advantages:

If done correctly, you’re not messing around with the vehicles electronics (too much). The modification can take place close to, or inside the light fitting.

Replacing a filament light bulb with an LED light bulb, can sometimes cause the vehicles electronics (or turn signal relay) to flash the turn signals faster than normal (hyper flash). The CAN bus system (vehicles electronics) can also think there is a bulb failure.

Installing load resistors will mimic the filament light bulbs load on the system. The turn signals will flash at the correct speed, and the CANbus system should also thinks the light bulb load is correct and not report any errors.

Disadvantages:

You will need a load resistor for each light fitting (are side indicators, wing mirror indicators fitted (leave as they are?). This could mean between 2 and 6 load resistors, dependant on the number of lights upgraded (just update the rear lights?).

Load resistors can generate heat, so they may need to be installed in a ventilated area, nowhere near anything that can burn or melt.

CAN bus Compatible LEDs:

CAN bus LEDs will not stop your turn signals flashing too fast (hyper flashing). They are designed to be compatible with a vehicle’s CAN bus system and prevent bulb failure warnings and error messages (sometimes produced by standard LEDs, because of the change in load on the vehicle’s electrical system). CANbus LEDs may be useful for non turn signal applications.

More Info:

Installing LED Load Resistors: