Troubleshooting No Trailer Brake Lights When Head Lights On After Prodigy Brake Controller Install

Question:

I hooked up my prodigy controller. All works fine. Except with my lights turned on running an headlights everything still works except brake lights on my trailer. Also with the truck off just sitting i get some intermittent rear trialer lights that fkash until it goes to standby or sleep mode. I have brake lights with truck headlights off but at nite no trailer brake lights. Also cant adjust trailer brakes from controller with lights on. It goes straight to 14 on display when i push pedal. Maybe a ground issue i dnt know. Thanks

asked by: Shawn

Expert Reply:

That sounds like a ground problem on your trailer. With the excessive draw of your headlights being on and then applying the brakes to turn on the rest of the taillights the insufficient ground problem rears it's ugly head and prevents the brake lights from illuminating.

I would check the grounds on the tail lights of your trailer and make sure they are making a good connection to a clean metal surface. A lot of taillight assemblies ground through the mounting hardware. If this is the case you need to make sure the assembly is attached to a clean metal surface.

If the assembly grounds does not fix the problem I would start checking all the grounds to all the circuits involved. The ground on your vehicle battery, the ground for the brake controller and the ground for your trailer connector.

I attached an FAQ on trailer wiring and brake controller installs for you to check out.

expert reply by: Jameson C