Troubleshooting Trailer Wiring Where Brake Lights Come On with Head Lights

Question:

I have a 94 Pete with a 07 Timpte grain trailer and I have all my lights but when my lights are on so are my brake lights. With my lights on I dont have brake lights. I checked continuity and I have continuity from my brake lights tale lights ground and marker lights. What should I have continuity between if Im checking on the truck side of things?

asked by: Bob

Expert Reply:

It sounds like the running light and brake light circuit of your setup is shorting out together somewhere on your setup. Either on the tractor side of the connector or on the trailer.

You can test the trailer connector with your circuit tester to see if both the pins are operating independently of each other like they should. If they both are coming on when the headlights are on then the problem is on the truck side of the wiring and you would need to look for a short somewhere before the connector. If it appears to function properly on the tractor then the issue is on the trailer side and you would have to check out the wires looking for any cut or exposed wire and fix as needed.

expert reply by: Jameson C