Troubleshooting Trailer with Bad Running Lights

Updated 07/06/2018 | Published 07/04/2018

Question:

I have working torn signals, brake lights, and flashers. But when I turn on my head lights. The trailer lights dont light up

asked by: Chuck W

Expert Reply:

There are a few things that could be going on. The first thing you want to do is isolate whether the issue is on the vehicle or the trailer. Start by using a circuit tester, like part # PTW2993, to test each function on the trailer connector at the back of your vehicle. If the running light circuit isn't working here, then the problem is on the vehicle. In which case start by checking the connector for any debris or damage as well as any trailer related fuses. Also, make sure the ground wire on the trailer harness is connected to a good, clean, bare metal surface. If all of these are good, you need to inspect the wiring starting at the connector and moving towards the front of the vehicle. Look for any pinched or damaged wires. Also, inspect the connector where the harness plugs in to the vehicle's wiring.

If the vehicle connetor all checked out then the issue is on the trailer. Here you basically want to check the same things; inspect the connector for debris or damage, make sure the ground is good, and follow the wiring from the connector to the lights looking for damage.

If you still can't solve the problem let me know what you found while troubleshooting and we'll go from there.

expert reply by: Charles S