LED tail lights hyper flash

[Dave001]

So replaced oem LED tail lights with aftermarket LED for the looks.

they will flash normally 2-3 times and then hyper flash.

I know theres all kinds of resistor modules out there for halogen to LED conversions, but here I only need to add a small amount of resistance to fix it.


Any advice on what kind of resistor to use?

 

[For The Popcorn]

Look for a flasher module designed for LED bulbs. That will solve the problem.

 

[Diver300]

Look for a flasher module designed for LED bulbs. That will solve the problem.

Flasher modules don't really exist in modern cars. In just about all cars made this century the flashing is done in one the ECUs.

As the OP is in the USA, I assume that this is about the bright red lights that are used for both brake and turn signals.

Almost all incandescent indicators or lights used as indicators are 21 W, so they take about 1.5 - 2A. The OP will need a resistor that takes about 1.5 A, so somewhere around 8.2 Ohms. It will have to be rated at more than 21 W. I would suggest a 50 W resistor. It needs to go in parallel with the lamp.

It's a legal requirement to detect that the turn signals are working. Putting a resistor in parallel with the lamp will stop that detection happening.

Some modern cars will have separate outputs for each lamp, and a higher resistance, lower power resistor may work.

Some combined brake/tail light assemblies will take most of their current from whichever supply is at a higher voltage. If the turn signals work correctly with the position lights turned off, you could try putting a diode in series with the position light wire, which will reduce the voltage to the position lights a bit, and make the assembly take more current from the brake/turn wire when that is on.

 

[For The Popcorn]

Flasher modules don't really exist in modern cars.

The behavior described is what happens with LED bulbs on thermal-style flasher modules. If the bulbs are controlled and monitored by a computer module, they should flash normally but pop up a message about being out – the OP made no mention of any error messages.

Maybe it's a flasher module problem, maybe it's the load the bulbs draw.

What kind of car is it?

 

[Diver300]

20 or 30 years of flashers units going twice as fast when a bulb fails has led to fast flashing being the de-facto warning that people understand, so there are a lot of modern cars that do fast flashing to show that direction indicators aren't working. There are some cars that will fast-flash the tell-tale on the dashboard but leave the remaining actual direction indicators flashing normally if one fails.

Edit:- I've just checked on my wife's car. It's so old that it's got a real key, and if it fails to start, you have to turn the key all the way back to try again, and there's a mechanical stop to prevent you trying to start it again.

The indicator is 16 W, so it only takes about 1.2 A. If I wanted to fit LED lights, I would need a resistor of about 12 Ohms to put in parallel.

It runs the indicators from an electronic control unit of some sort, not a flasher unit. When the bulb is removed, the indicator at the other end of the car continues to flash at the same rate, but the tell-tale on the dashboard flashes twice as fast. There is no other warning of the failed indicator. Also the tick sound stops if there's some other warning sounding. I'm fairly sure that a flasher unit wouldn't behave like that.

 

[Dave001]

Flasher modules don't really exist in modern cars. In just about all cars made this century the flashing is done in one the ECUs.

As the OP is in the USA, I assume that this is about the bright red lights that are used for both brake and turn signals.

Almost all incandescent indicators or lights used as indicators are 21 W, so they take about 1.5 - 2A. The OP will need a resistor that takes about 1.5 A, so somewhere around 8.2 Ohms. It will have to be rated at more than 21 W. I would suggest a 50 W resistor. It needs to go in parallel with the lamp.

It's a legal requirement to detect that the turn signals are working. Putting a resistor in parallel with the lamp will stop that detection happening.

Some modern cars will have separate outputs for each lamp, and a higher resistance, lower power resistor may work.

Some combined brake/tail light assemblies will take most of their current from whichever supply is at a higher voltage. If the turn signals work correctly with the position lights turned off, you could try putting a diode in series with the position light wire, which will reduce the voltage to the position lights a bit, and make the assembly take more current from the brake/turn wire when that is on.

I'm not doing a incandescent to LED conversion, its a OEM LED to aftermarket LED conversion. So the common "anti hyper flash resistor modules" all over Amazon won't work, as it will be too much resistance. Correct?

 

[Dave001]

The behavior described is what happens with LED bulbs on thermal-style flasher modules. If the bulbs are controlled and monitored by a computer module, they should flash normally but pop up a message about being out – the OP made no mention of any error messages.

Maybe it's a flasher module problem, maybe it's the load the bulbs draw.

What kind of car is it?

I'm not doing a incandescent to LED conversion.

Yes it does trigger a error message on the dashboard.

Vehicle is a 2021 GMC sierra

 

[Dave001]

Oh and the OEM tail lights when plugged in it works just fine, so its not an issue with the vehicle.

 

[Diver300]

I'm not doing a incandescent to LED conversion, its a OEM LED to aftermarket LED conversion. So the common "anti hyper flash resistor modules" all over Amazon won't work, as it will be too much resistance. Correct?

You will probably need the resistors to take less current than would be needed for a conversion from incandescent. Less current means that you need a higher resistance.

However, as the OEM LED could be a wide variety of circuits, and could even have communication protocols to the real lamps, more information would be needed.

The first step would be to measure the current for the OEM and the replacement lamps.

 

[Reloadron]

Almost all incandescent indicators or lights used as indicators are 21 W, so they take about 1.5 - 2A. The OP will need a resistor that takes about 1.5 A, so somewhere around 8.2 Ohms. It will have to be rated at more than 21 W. I would suggest a 50 W resistor. It needs to go in parallel with the lamp.

You nailed it perfectly. Give this a look, we go with about 6 to 8 ohms and a 50 Watt resistor on motorcycle conversions to LED from incandescent lamps.

Yes, I know this is not what the thread starter is after.

Ron