Troubleshooting Non-Functioning Brake Light on Driver Side

Question:

I have changed the socket the bulb and the switch at the pedal. I have also checked the circuit on the plastic assembly it does not appear that the problem is in the tail light assembly what do you suggest

asked by: Steve S

Expert Reply:

Are you referring to the brake light on your vehicle, rather than on the trailer? If yes, check your engine compartment power distribution box to see if there is a blown fuse for the brake light circuit.

If you are referring to the brake light on your connected trailer those lighting signals come from the wiring harness in the tow vehicle but you can test the trailer lights directly by disconnecting the trailer and applying 12V power directly to the trailer connector's contacts to see if the lighting functions operate properly. If they do not work when given direct power in this manner then you need to check the wiring from the trailer connector all the way back to the non-functioning light, looking for signs of cracked or worn insulation.

Make sure the light has a good ground, whether it's through a ground wire or through one of the mounting studs. Clean or sand the grounding point to ensure a clean bare metal to metal connection.

If they do work, then you need to test the vehicle's connector with a circuit tester like # PTW2993. Have a helper activate each function while you apply the tester to the appropriate pins; please see the linked article for help identifying the correct pins to test for each function. The video shows how to use the tester.

Please tell me about your vehicle (year/make/model/version) and if it is the vehicle or trailer lights you are referring to.

expert reply by: Adam R