Led tail light issue

[andrewwynn]

Originally Posted by tommy2704

can i not just put a resistor into the light circuit and if so what resistor do i need.

You have used a couple confusing terms that don't match standards.

You have been calling the "run/ning" light circuit the "light" circuit they are all light circuits.

The run circuit runs at full voltage and is incompatle with your lighting. Wire a 24 Ω resistor from that wire to ground.

You may still get an error because the brake lamps also don't pull enough power in which case you would need to wire a lower resistance resistor in parallel to the BRAKE circuit (which is actually run/brake circuit. ).

I would need to know what amount of current the circuit pulls when lighting both top and bottom to know the correct resistance to emulate the 21w filament but people usually use 6 Ω. It likely needs closer to 8-10 Ω but only trial and error will determine what level will prevent the error.

The problem is two fold:

1) you don't have run wire connected at all the car correctly identifies this as a blown filament.

2) the brake circuit has too low of resistance even when doubting up the lamps, so it will likely see this as a failing filament.

If you know the wattage of the LEDs or can measure the current going to get fixture when the brakes are applied I can do the math to tell you the proper resistor.

A 6 Ω resistor at 12v is 24w! That's similar to a small soldering iron so it needs to be a special metal resistor and should be touching metal to pull the heat out.

If you only need 10 Ω, the power drops from 24w to 12w or half so it's worth figuring out what is actually needed.

With any luck simply doubling up the lamps (which you did) will trick the car into thinking the lamp isn't blown.