Troubleshooting Trailer Tail Lights Not Working But All Other Lights Are Working Normally

Updated 06/15/2021 | Published 06/12/2021

Products Featured in This Question

Pollak Replacement 7-Pole, RV-Style Trailer Connector Socket - Vehicle End

(745)

$14.85

Hook Probe Circuit Tester

(66)

$14.36

Question:

What would make all the lights work but the tail lights

asked by: Fanessa R

Expert Reply:

If just the taillights on your trailer are not working, but the turn signals and brake lights are you will want to start with finding if the issue is on the tow vehicle or trailer.

Using a circuit tester like # PTW2993 test the 11 o'clock pin if you have a 7-way connector on your tow vehicle, or the pin right next to the ground pin if you have a 4-way connector as shown in the included diagrams. You will need to have the head lights of your vehicle on for this pin to have power.

If you do not have power the issue is on the vehicle side and is more than likely a blown/missing fuse. Check the engine bay fuse compartment to verify that the fuse is installed and not blown.

If you do have power, then the issue is on the trailer side. I would start with checking that the trailer connector does not have any debris or corrosion in it causing a connection issue.

Next check that all of the running lights have a solid ground that is not loose and is connected to bare metal. Some lights ground through the mounting hardware so you will need to make sure they are bolted to metal if this is the case.

I included a link to a helpful article on wiring for you to take a look at.

expert reply by: Samuel C