Troubleshooting No Trailer Brake Lights After LED Conversion

Question:

hello, I am wondering why there is not a single word on your entire website about resistors when it comes to diodes. I installed your led trailer lights on a 2000 ford taurus and everything works except my brake lights on my trailer. my high mount stop light on the car side is illuminated when depressing the brake pedal. do I need a resistor wired in parallel or series to fix the problem I have? oh and yes, my ground wire is securely attached, I have a good ground on car and trailer side. ground is not the problem, that much I do know lol thank you in advance for your response

asked by: Wesley

Helpful Expert Reply:

Resistors aren't generally required when converting a trailer to LED lights because there isn't the need to increase the amperage load like when doing the same conversion on a vehicle.

On a vehicle when you go from incandescent to LED you have to install the resistors so that the thermal flasher unit of the vehicle senses the correct amount of amperage draw to operate properly. There isn't a flasher unit on the trailer side of the wiring so the resistors aren't needed. The turn signal circuit for the trailer's wiring on the vehicle has already been generated once it gets to the trailer wiring.

Typically a resistor would only be needed on trailer wiring if the same circuit was powering both a LED and incandescent light.

I would use a circuit tester like part # PTW2993 to make sure that the circuit is getting 12 volts when the brakes are applied.

You said your ground wire is securely attached but you still might try running a jumper ground wire for the light when pressing the brake pedal just to rule that out totally. If the turn signals are working fine but the brake lights aren't that is almost always an insufficient ground since the two circuits are carried on the same wires and the only difference is that both circuits are active when brake lights are applied and there is more amperage draw on the vehicle as well.

I attached a couple help articles for you to check out as well.

expert reply by: Jameson C