Troubleshooting Trailer Brake Lights Not Working on 4-Way When Turn Signals and Running Lights Work

Question:

I was at a U-Haul store and I have a 4 wire system on my truck Im Curious as to why my Right Blinker and Left Blinker operate correctly. Parking lights/Side Lights work correctly. However when I press the Brake, the brake light on the trailer does not light up? Someone pulled in right after me hooked up their truck and everything worked correctly. HELP please?

asked by: John M

Expert Reply:

Without knowing exactly what truck and lighting you have John this is going to be a vague troubleshooting. First if your wiring is a factory setup you are going to want to start by checking your fuses as they will be independent for each lighting function. If you have an aftermarket setup you will want to start by checking the input going into your converter box using a Test Light # PTW2993. If you have an input signal going into the 4-way converter but nothing coming out then you know the converter is bad and will need to be replaced.

As I said these are vague tests. If you can let me know what truck you have and if you have factory or aftermarket wiring I can help you with more specific information.

expert reply by: Bud M