Have Running Lights and Trailer Brakes Function Properly but No Brake Lights or Turn Signals.

Question:

i have checked the harness on vehicle. with volt meter with blinkers on and im getting 12-14 volts both left and right. but when plugged into trailer i loose voltage to junction box on trailer. voltage on turn/brakes s through wire from truck to trailer junction box down to 0.4 volts. replaced wire on trailer. same problem. could this be a grounding issue? have checked wiring on trailer with 12 volt battery from junction box on trailer to the back of trailer and everything is brand new and working properly. I dont know where to go from here. Any ideas??

asked by: Dustin

Expert Reply:

Since all of the functions on the truck are working properly, and you have narrowed down the wiring problem to between the junction box and trailer connector, I believe you have a problem with the trailer side connector itself.

Check the inside of the trailer connector for corrosion. If you find green and/or white corrosion that will be where the problem lies. You will need to clean this corrosion out and make sure the connections are secure. Sometimes the corrosion is rather stubborn and the connector needs to be replaced. In this case I recommend replacing it with the 7-Way Molded Trailer Wire Connector, 3 foot, item # H20042, or if a longer length of wire is needed the 8 foot trailer wire connector, item # H20046.

You could also have a ground problem. If the trailer connector to the junction box is good. Make sure that the white wire from the trailer connector is securely connected to a clean, paint, rust and corrosion free part of the trailer frame, then check all of the lights for the same secure ground connection. You should also check the light mounting brackets connection to the trailer frame. If they are bolted on you will need to check them to be sure that there is no corrosion inhibiting the ground connection there.

expert reply by: Bob G