Troubleshooting a Left Trailer Light Not Functioning

Question:

All my lights on my trailer come on when I plug in. Now my left light does not brighten up when I hit the brakes or it does not flash when I turn on the turn signal but it flat out does come on and work......where do i start?

asked by: James W

Expert Reply:

First I would check the ground of the left tail light assembly. It sounds like the light is not getting a strong enough ground and because of that it is not illuminating. You will want to make sure that it is connected to a clean metal surface. If it grounds through the mounting hardware then you will need to make sure it is mounted to a clean metal surface.

Next check the back of your trailer connector on your tow vehicle, look for corrosion or exposed wire that could be causing a short and fix as necessary. Next I would check the front of the connector looking for any bent prongs or corrosion that need to be fixed.

Usually at this point we recommend you use a circuit tester like our part # 3808 to test the functions of your trailer connector on your tow vehicle. This will determine if the problem is on your tow vehicle or on your trailer. Check out the video I attached to see how this is done. If the voltage looks good on your vehicle connector then you know the problem is somewhere on your trailer wiring and needs to be inspected and fixed.

I attached an FAQ on trailer wiring for you to check out also.

expert reply by: Jameson C