All Trailer Lights Work Except Running Lights on New 4 Wire Light Kit

Updated 08/02/2010 | Published 07/29/2010

Products Featured in This Question

(66)

$14.40

Question:

Installed new wiring kit for boat trailer. all wires checked, ground checked all lights work except running lights. Are wires checked with VOM.

asked by: Ronnie

Expert Reply:

You can check the wiring with a multimeter, but usually a basic circuit tester is enough to diagnose the problem.

The first step we recommend is isolating the source of the problem to either the vehicle or the trailer by checking the vehicle side connector. Disconnect the trailer from the vehicle. Using a circuit tester, like part # PTW2993, or multimeter, check the 3 pins on the vehicle connector while using the 4th pin as the ground. Yellow should be left turn and brake, green should be right turn and brake, and finally brown should be the taillights. If your circuit tester lights or your multimeter reads around 12V, then the vehicle is fine, and the problem is on the trailer. If it does not check out, then you need to trace the vehicle wiring.

Some of the trailer lights on the market are stud grounded and some have wire grounds. Make sure that whichever version you have, the ground connection makes good contact with clean metal. Rust and paint can insulate your ground connections. A bit of sand paper can remove the paint or rust and allow continuity. Also make sure the ground lead on the trailer connector is connected to good, clean metal on the trailer frame.

Which trailer light kit do you have? If I know what kit you have, I may be able to provide some more specific help.

expert reply by: Patrick B