Brake Lights Do Not Work When Brake Pedal is Pressed  

Question:

Expert Reply:

It sounds like there is a bad plug-in connection or a weak ground on the trailer side or vehicle side. Make sure the two plugs are free of any build up or corrosion because that could be causing a poor connection between the connectors.

If the plugs are seated properly and you still do not have brake lights it is most likely a weak ground. Check the grounds on both the trailer side and vehicle side. The ground needs to be connected to a clean bare metal surface to properly ground the current. Most of the time, a weak ground causes some functions to work while others will not. In your situation, the running lights are working but not the brake lights. It sounds like the ground is too weak to support both functions. It is also a good idea to check the ground connection behind each taillight as well.

If it turns out the grounds are okay, then you need to isolate the issue to either the vehicle or trailer. You can isolate the issue by testing the connector on the vehicle using a circuit tester like part # PTW2993. Someone will need to sit in the vehicle and run through each function while someone uses the circuit tester at the rear of the vehicle to check for power. If the vehicle connector is getting power, the problem is the trailer wiring.

It is a good idea to check the trailer wiring for any damage or pinched sections of wire. Traditionally the green wire powers the right turn/stop function, and the yellow wire powers the left/turn stop function, but they could be different colors on your trailer.

If these suggestions do not fix the light issue, please let me know and I can help you troubleshoot further.

expert reply by: Heather A

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