On the 3rd brake light above the cab back window the drivers side red light won’t turn off when you turn the ignition off. A new bulb was put in and the wiring checked but the Ford dealer cannot find the cause or fix it. Help!
Has anyone tried unplugging the brake light switch at the brake pedal to see if the light goes off?
If there’s no visually obvious short circuit at/inside the fixture, could be a body control module problem. The BCM is a self-contained computer that connects directly to various switches, bulbs, and to the drivetrain computer (PCM). From what I can tell the brake light switch is an input to the BCM, and the bulb power signals are outputs of the BCM. Was there any electrical work done just before this symptom appeared? If so the BCM might have been inadvertently damaged by static electricity build-up during the work. Jump-starting activities (giving or getting) could also be a cause. You might try disconnecting the battery overnight, that will reset the BCM upon reconnection the next AM.