Trailer Lights Very Dim, Running Lamp Circuit Isnt Working  

Question:

Helpful Expert Reply:

It sounds as if you have two separate issues happening, likely a poor ground for the trailer connector on the tow vehicle, as well as a broken or loose connection in the running light circuit on the trailer.


I'd first check the ground connection to the vehicle for the trailer connector on the tow vehicle. Make sure this connection is securely made to bare metal, and check that the connection isn't corroded.

Next, you'll want to track down the running light problem. Use a circuit tester like # PTW2993 on the trailer connector pin for the running lights (fed by the brown wire) while the vehicle headlights are switches on. IF the tester lights up, then the problem is in the wiring on the trailer. If it doesn't light up, then check the brown wires entering the converter box. If there's power going into the converter box but not leaving it, then the converter is bad and should be replaced.

Before replacing the converter, you'll want to locate and repair the problem in the running light circuit on the trailer so you don't continue cooking taillight converters. Begin at the 4 pole connector on the trailer, make sure its not damaged or corroded. Make sure the trailer connector is securely grounded to the trailer frame to clean metal that's not corroded. Trace the running lamp circuit (usually a brown wire) back to the taillights, making sure nothing's pinched or loose. Make sure each lamp is grounded either through it's mounting studs to clean metal on the trailer frame or via a separate ground wire.

These are the common 'culprits' to check. I'll link to a help article that will help troubleshoot trailer wiring problems.

expert reply by: Mike L

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