Trailers Left Turn Signal and Left Brake Light Do Not Work

Question:

Trailer parking lights work sometimes. Left trailer light stays on left signal does not work nor does the brake light. Can I bypass the powered wire harness.

asked by: Steve

Expert Reply:

I wouldn't recommend bypassing the converter box becuase it's there to protect your vehicle's wiring from shorts. Also, the wiring harness isn't the likely solution to the problem. And if the problem is with the converter box on the wiring harness then you'll want to find what caused the converter to go out in the first place. Which would likely be a short in the trailer's wiring.

You'll first want to test the trailer connecter on the back of your tow vehicle. Use a circuit tester, like # PTW2993. Also, make sure the connector is free of any dirt or corrosion. If everything checks out here then the problem isn't the converter because it's on the trailer side. If the problem is on the vehicle side, you'll want to test before the harness. If the problem is the harness I would replace it, if not then you'll need to inspect the truck's wiring, or have a mechanic do it.

If the trailer is the culprit inspect the connector on it for dirt and corrosion. Then you'll want to check the wiring all along the trailer looking for pinches or damaged points. This is likely where the problem is. Also, inspect the ground wire and the ground locations. Including if the lights are grounded through the mounting studs.

If you still can't locate the problem let me know what you have found and we'll do more troubleshooting.

expert reply by: Charles S