Troubleshooting Trailer Running Lights Not Working with New 7-way Adapter

Question:

I have a 2010 ford F-150 pickup which has a 4-flat trailer hookup. just purchased a popup camper with a 7-way plug. I purchased a 4- flat to 7-way adapter and hooked it up to get brake lights and signal lights according to instructions, it worked but i have no side running lights. I have a blue, yellow, and black wire left over which are for electric brakes, auxiliary and backup lights. If i hook up the remaining wires will that fix my running lights. I would appreciate your input. Thanks.

asked by: Melvin P

Expert Reply:

Connecting the 12V power, electric brake output, and reverse functions will not fix the running light issues on your 7-way. It is very likely that when one function isn't working properly that there is a bad ground that is allowing some functions, but not strong enough for all signals. Sometimes this is due to rust or corrosion, other times it just needs a bare metal to metal connection for stronger signal. I'd start there and if that doesn't solve it, check your vehicle fuses. If the fuses are good, use a circuit tester like # PTW2993 to test each function and ensure you have a signal at the running light pin when the trailer is not connected. If not, trace that wire with the circuit tester to find the short and replace the wire as needed.

If the connector works well on the vehicle side, then clean both the vehicle side and the trailer side of the connector and add some dielectric grease # 11755 to the connection. I've attached an article to give details, but it basically keeps moisture and debris out of the connection to assist in power transfer.

If your trailer is the issue, then you can use a 12V battery to test each function and use a jump wire for the power and ground. If this works, then your ground is the issue and should be moved. Some lights use the mounting hardware as a ground, so you can use the jump wire to see if that mounting ground needs to be improved. If not, use the circuit tester to trace the running light function on each side and replace wire as needed.

expert reply by: Jason S