No Function on any Right Side Lights on Trailer Behind 2010 Subaru Forester  

Question:

Expert Reply:

I have found the best way to find a bug in an electrical system is by process of elimination. Eliminating possible sources will eventually lead to the right spot.

First thing I would do, is check the 4-Way connector on your Subaru Forester. Using a circuit tester like part # PTW2993 or a 4-Way tester like part # F5CT or part # I26. The white wire is ground, the yellow wire is left turn and brake, the green wire is right turn and brake, and the brown wire is taillights. Chances are, the vehicle or vehicle connector is not your problem, but double check so we can eliminate it as the source for certain.

It sounds like you have a ground problem on the trailer since it is knocking out a whole side. Check to make sure the grounding connections for the light have good metal to metal to contact. Paint or rust on the trailer frame can act as an insulator, preventing a good ground connection and ultimately leading to lights doing all kinds of screwy things. Check the white ground wire at the connector on the trailer. Trace it back and see where it attaches to the frame. If it only runs to the left side, try splicing in a piece of wire and running that to the right side. A cracked weld along the frame between the lights and the ground wire connection could even cause a bad ground.

If you are satisfied that the ground connections are good, check the wiring for the lights. Trace all the wires. Look for pinches, nicks, and fraying. If the wire got down into the suspension area, it could easily be pinched or cut, breaking the connection.

Check these things and write back and let me know what you find. If you have not found the source of the problem, we can check some other things.

expert reply by: Patrick B

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