Headlights Tail and Brake Lights
Jeep Grand Cherokee Limited
Honda Accord EX

How do you fix brake lights that don't work The 3rd brake light functions but the tail light bulbs don't when the brakes are applied They do function as tail lights but not when the brake is applied?

Answer

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Wiki User
October 29, 2006 6:45AM

Probably bulbs. There are 2 filiments that are in the tail/brake lights. One for the tail and a second brighter one for the brake. Try replacing the bulb on one side first and check it. ==Additional Information== It is highly unlikely that the brake light filiments in BOTH bulbs would fail [burn out] at the SAME time. Although there are several possible causes including wiring, connectors, brake light circuit fuse, and others, BUT since BOTH lights are not working, I suspect that the MOST PROBABLE cause is a MISADJUSTED brake light SWITCH. I would first replace the brake light circuit fuse with a KNOWN good fuse. If that does not correct the problem, the brake light switch should be your next component checked. Next, I would properly readjust the brake light switch. The switch is adjusted by means of a threaded neck on one end of the switch, from which the actuating "plunger" protrudes. That threaded neck screws into and out of a threaded hole in a bracket which usually is mounted on a bracket to, or the metal frame for the dash board/instrument panel. When the plunger is fully pushed into the switch, the contacts are pushed "open," preventing flow of electrical current to the brake light wire[s] to the bulb filiments. When the plunger is released and allowed to fully extend, the switch contacts close, allowing current to flow to the filiments. When the switch is PROPERLY ADJUSTED, and the pedal is fully retracted ["back"] the brake pedal arm holds the plunger fully in, and therefore, the switch "off." When the brake pedal is depressed, it moves away from the switch allowing the plunger to extend and the switch to close, turning the brake lights on. Both lights are fed through the same switch and wire harness to the split to the two bulbs, and again, BOTH being out simultaneously suggests the switch, or it's adjustment, may be at fault.