Diagnosing Trailer Wiring Problem on 1995 Nissan Pickup

Published 05/04/2011

Question:

I have a 1995 Nissan PU I bought used and a brand new trailer I just bought for it. when I initially hooked up the trailer to the wiring connector that was already on it, only the tail lights of the trailer lit up, not the brake or turn signal. I took the old wiring kit off a generic that had been spliced in, reconnected all the wiring so that the truck lights all work properly, and installed a towready adapter made for the Nissan. But now none of the lights on the trailer work, though all the truck lights work. Is this a grounding problem?

asked by: Ian M

Expert Reply:

A ground problem is a possibility but having an insufficient ground connection usually causes the trailer lamps to behave erratically, or to work properly until the vehicle headlights are switched on.

The best place to start would be to use a circuit tester like part # PTW2993 and test the trailer connector as each function is tested. This will tell you if the problem exists on the vehicle or the trailer.

If your testing shows that the trailer connector is functioning properly, then you know that the problem is in the trailer wiring. If this is the case, you will have to trace each circuit from the trailer connector back to each individual lamp. Start at the connector itself, and ensure noting is damaged or corroded. Make sure that the ground connection which is typically on the trailer tongue is securely attached and is not corroded. As you trace each circuit back from the trailer connector, look for pinched wires and cracked or missing wire insulation. Check that each lamp is securely fastened to the trailer frame and that the mounting points for the lamps are not corroded, as many lamps receive their ground connection from the mounting studs, not a separate wire.

If your testing shows that you are not receiving signal at the trailer connector, you will need to test the converter itself. Use your tester to ensure that you have power entering the converter on the input side and leaving on the output side. If there is power going in but not out, the converter is damaged and should be replaced. Also check to make sure the ground connection from the converter is securely attached to the truck chassis, and that the connection is made to clean, non-corroded metal. If the converter needs replacement, before replacing it you should closely examine the trailer wiring to locate the short that caused the converter to fail.

If there is not power reaching the converter, review your connections to the taillight assemblies.

expert reply by: Mike L