Hello everyone! I have recently acquired a GMC Thomas Built short bus. None of the rear lights work(brakes nor tail lights). I did replace the brake light switch but still nothing works!
Any help would be greatly appreciated. Thanks!
1) While unlikely it is possible that all of the bulbs are just burned out.
2) The fuse(s) are blown (possibly due to a short circuit).
3) The ground connection on each fixture is bad.
4) The wiring harness powering the lights is cut/disconnected, or has at least one short circuit in it.
Do the front parking lights/marker lights/clearance lights come on? Do the rear clearance lights come on?
Pull the bulbs first and check that they are not burned out. Then locate and pull the fuses and check that they aren't blown. The next step would be to take a multimeter and turn the parking light switch on, and check for voltage in each of the sockets.
Replacing the brake light switch will only affect the brake lights... have someone step on the brake pedal while repeating the test on the brake light connectors.
If you get no voltage on multiple connections you'll need to find the other end of the wiring harness and check for continuity and/or short circuits.
When you bought the bus, perhaps the seller (a school?) mechanics went to disable the lights that flash when stopping to pickup children.
Perhaps they disconnected the brake and turn lights by mistake.
Again, look in the electric panel mentioned above.