Troubleshooting Clearance Lights Trailer Wiring

Question:

My brakes turn signals and hazards work but when The running lights are turned on the clearance lights on the trailer intermittently blink Where is supposed to keep a constant late at all times. Why is this?

asked by: Henry P

Expert Reply:

I'm not sure why but I can give you some steps to troubleshoot; in order to determine the specific problem you will need to purchase a circuit tester if you do not have one - the very handy Cordless Circuit Tester # PTW2979 - and test the connector on your vehicle after disconnecting it from your trailer.

Check the wiring going into your harness from your tail lights to see if those wires are carrying the correct signals, if not then the issue is with the vehicle wiring. If the signals going to your harness are okay, you'll need to test the signals coming out of the harness, and if they are correct then your issue is likely going to be with the trailer side wiring. You will also want to check both your vehicle and trailer connectors for corrosion, which can be green or white in color. A build-up of corrosion can interfere with the signals getting through the connectors so if it is present you are going to need to replace the plug with # 18004 for the trailer side. You'll also need to make sure your grounds are attached to bare metal surfaces and free of any paint, dirt or corrosion.

I have added links below to a pair of help articles on trailer wiring, including a troubleshooting guide for you to take a look at. Additionally, to help prevent any type of corrosion in your connector, and increase its durability and lifespan I highly recommend using Dielectric Grease for Electrical Connectors # 11755.

expert reply by: Kyle S