Brake Lights on 2012 Semi Trailer Work But Not Brake Lights on 2004 Freightliner

Question:

brake lights are lit up on 2012 semi trailer but not on 2004 freightliner we are not using the brakes trying to make them go off checked connections make sure wires wher not crossing any ideas all other lights work like there supposed to

asked by: Max R

Expert Reply:

Since your semi trailer brake lights are working but the tractor's brake lights are not working, it sounds like the wiring for the trailer lighting is independent of the tractor's brake lights. If all of the trailer lights operate as they are supposed to then I would first check the fuse panel in the tractor for a blown brake light fuse or perhaps for corrosion in the fuse holder. You can also check the individual brake lights on the tractor for signs of a weak ground connection (especially if they are the stud mount type that use the stud for the ground).

expert reply by: Adam R