Diagnosing Lighting Problem on Trailer Towed by 1995 GMC 1500 Pickup

Question:

My turn signal, brake light, and running light is working fine on the right side of my trailer but the left side has nothing at all. Attached a tester to the trailer connector on the truck and both running light and left turn signal did not light up. This is on a 4 point connector. I replaced the plug on the truck that connects to the tail lights of the truck to the trailer hook up. All lights on the the truck are working fine as well. I also checked the trailer ground wire and the ground on the truck-trailer hook up. I do not know if a fuse would cause this or another ground wire I do no know about.

asked by: Keith E

Expert Reply:

If your truck is equipped with the factory tow package, there will indeed be fuses that protect the towing circuits that might be blown. Your owners manual or the legend printed on the lid of the fuse box should list the fuse location that you are looking for.

If you do find and replace a blown fuse, you will then need to closely examine the wiring on the trailer to locate the short that caused the fuse to blow. Make sure the connector on the trailer is not damaged or corroded. Trace each circuit making sure that there are no pinched wires, or cracked or worn insulation that would allow the copper conductor to short out on the trailer frame. Make sure the ground wire from the trailer connector is securely grounded to the trailer frame.

Most likely, you are dealing with a blown fuse.

expert reply by: Mike L