Troubleshooting Rewiring Of Tail Lights And Running Lights On Trailer

Question:

I recently rewired the lights on my trailer and added 2 markers on the side. Problem is the markers don't work and in back I have turn signal and brake lights but at night when I turn the headlights on the rear lights don't come on. Yet I still have brake and direction lights working.

asked by: Raymond S

Expert Reply:

There are a few troubleshooting steps to help you figure out why your lights are not working.

A trailer's brake and turn signals are on one circuit and the running lights are on another circuit. This is why you still have turn and brake signals but no running lights. The problem is the running light circuit.

To find the issue, I would start by making sure the issue is either the trailer side or the tow vehicle side (you may have already done this). Use a circuit tester like Item # PTW2993 to check the connector on the back of your vehicle. If the running light circuit does not work, then the problem could be a fuse. If the vehicle side checks out, then you know for sure that the issue in on the trailer side.

If it's the trailer side, then make sure that it does not have any corrosion or debris "gumming up" your signal. If you have a 4-way connector, the pin for the running lights is the third one or the closest one to the ground. If you have a 7-way connector, it's the blade in the 1 o'clock position.

If the pin is okay, then you will need to inspect the wiring coming out of the connector all the way to the lights. Trace the running light wire and see if you find any damaged, pinched or disconnected wiring. If you connect the trailer to your tow vehicle and turn the running lights on, you can use the circuit tester by probing the wire as you trace it to see where the problem begins along the circuit.

If still having issues, let me know and we can keep troubleshooting until we find it.

I have attached a few articles regarding trailer wiring that might help.