Lights Not Working on Camper Towed by 2004 Ford F150 Using 4-Pole To 7-way Adapter

Question:

im trying to pull a camper trailer with my 2004 f150 with a 4 flat to 7 round rv adapter, but when we hook up the trailer there are no exterior lights brakes, turn signals, running lights. but when we hook it up to a van with electric brakes and 12v everything works just fine. we tested all the connections on the truck and the adapter is getting power and we have a good ground. what might cause this to happen?

asked by: Brad

Expert Reply:

You said that the adapter is getting power, but is the 7-way on the adapter putting out power on the lighting circuits? You'd need to use a circuit tester like part # PTW2993 on the 7-way as each taillight function is activated, to check it.

If the 7-way on the truck tests out okay, but won't work on the trailer (which works on other vehicles) try using the truck with a different trailer if possible. This will 100 percent rule out the truck as being the problem.

You still might have a ground problem, even though the trailer worked okay on another vehicle. Some vehicles are more sensitive about trailer ground problems than others. Thoroughly check the trailer ground where it connects to the trailer frame. Make sure this connection is made securely to clean un-corroded metal. Each trailer lamp should be grounded by a separate ground wire that's connected to the frame, or by its mounting studs being in direct contact with the trailer frame.

I'll link you to our trailer wiring troubleshooting FAQ article, which I hope you'll find helpful.

expert reply by: Mike L