Troubleshooting Only Left Indicator Light Flashes on Trailer

Question:

Trailer lights have worked fine for years, until recently. Both the left and right indicators only flash the left indicator light so left indicator on the car flashes left on the trailer, and right indicator on the car flashes left on the trailer too. The right indicator light won’t signal at all. The hazards are also only flashing the parking lights, rather than the two indicator lights. I replaced the 7-pin plug on the trailer side, and got the mechanic to run diagnostics on the car, but we still have no right indicator!

asked by: Sarah H

Expert Reply:

It sounds like you've ruled out the vehicle along with the trailer side connector which doesn't leave much to check. Then again, I'm not 100% sure what diagnostics they ran on your vehicle so it wouldn't hurt to double check the vehicle connector. Make sure no corrosion or debris is present. Assuming that is fine, double check the pins for your signals using a circuit tester like # PTW2993. After that I would be looking at the ground connection on the trailer. Make sure it is secure on a clean, bare metal surface. If your ground is good then I would check for a short.

expert reply by: Robin H