Utility Trailer Brake Lights Not Working

Updated 10/27/2020 | Published 10/22/2020

Question:

Hi I have a utility trailer and the brake lights arent working but everything else works oys just the brake lights. I was wondering if you know what it could be thank you

asked by: Sabrina

Expert Reply:

We should be able to easily sort out the issue with your non-functioning brake lights. As a primer, I posted a link to a trailer wiring FAQ article. Take a look at that before we start.

First, we need to determine if the issue is on the tow vehicle side or trailer side. Unplug the trailer from the vehicle and on the vehicle connector use a multimeter to measure for 12 volts on the brake light pin. If you don't have a multimeter you may want to order the Performance Tools # PT89ZR . From the trailer wiring article find your style of connector and it will identify the brake light pin.

If you don't have 12 volts on that wire you will need to trace the wire back looking for nicks, cuts, or broken wire. Also inspect the connector that the brake lights connection pin(s) is clean and not corroded. Also be aware of in-line fuses that attache to the wire. Also, check your owners manual to see if there is a fuse in the vehicle fuse panel.

If you do have 12 volts at the vehicle then the issue is on the trailer side. Check the connector that normally plugs into the vehicle. There should not be any dirt or corrosion. Next check the voltage at the tail lights bulb sockets. If you have 12 volts there, then check the grounding for those lights. Many of these lights ground to the trailer frame where they are mounted with the same screws that hold the light housing to the frame. Clean off any corrosion found there.

Just for good measure, find the main trailer frame ground. From the connector at the front of the trailer find the white ground wire. Follow it to it's nearby location where it is screwed to the frame. A loose or dirty connection here can cause all kinds of issues. I would disconnect it clean all parts and ensure there is a bare metal connection on the trailer frame. Just a screw connection is not always sufficient.

All these steps assume that you have tail light working as running lights and blinkers, but not as brake lights. If the tail lights are not working at all check to see if the bulbs are blown and if there is any sign of water intrusion. If so, install new bulbs, clean all contacts, and when the problem is resolved caulk all of the seams.

If you continue to have issues email me back for more troubleshooting.