Originally Posted by
David T
My vote is for the taillight boards and bulbs. Because of the intermittent nature of the problem it tends to be bad connections. I agree to start at the brake switch to "divide and conquer". Wherever the power comes from it has to be on the switch. Once you verify you have power at the switch you jumper it and see if you can get the brake lights to light up. Don't forget, just because you have power at the taillight boards (if in fact, you do), you also MUST have a good ground to complete the circuit.