Brake Lights on Trailer Do Not Work But All Other Lights Work

Question:

my running lights work an my turn signals work, but have no brake lights either side

asked by: Mike R

Helpful Expert Reply:

The most likely problem is a bad ground. A bad ground will appear when there is more load on a system. In this case the brake lights which light up brighter and constant have more load than do turn signals or running lights. The first thing to check is the trailer connectors on the vehicle and trailer. Make sure they are clean and free of corrosion. That might be all it needs.

If you still have problems then use a circuit tester like # PTW2979 if needed and check the functions on the vehicle side connector. If the signals are all working then you know the problem is on the trailer. If not then the problem is on the tow vehicle. Check the stop light or CHMSL fuses to see if they are blown or missing.

On the trailer, make sure the main trailer connector ground is attached to a clean and corrosion free bare metal surface. Then do the same for each of the trailer lights.

helpful expert reply by: Michael H