All vehicle brake lights use a switch to determine if the lights are on or off. This switch, known as a stoplight switch, consists of a plunger-style button that breaks and completes a circuit. When the brake pedal is pressed, the plunger comes outward, completes the circuit and the lights turn on. There are several faults that can make your brake lights stay on. The circuit may go bad and remain completed, or the rubber stopper on the brake pedal stalk could fall off or come apart. If nothing is keeping the plunger pressed in, the circuit remains open.
Push the driver's seat as far back as possible, allowing you to lay on the floor on the driver's side.
Shine a flashlight at the top of the brake pedal stalk and find the stoplight switch. It will be a plastic cube either connected to the brake stalk or directly opposite the brake stalk, depending on the vehicle.
Depress the brake pedal and feel where the brake light switch contacts the stopping plate, a metal plate in direct line with the stoplight switch.
Feel for an open hole where the stoplight's plunger-style button presses. If a hole is present, you simply need to replace the rubber stopper.
Press and release the plunger-style button on the brake light switch and ask an assistant if the brake lights are turning off and on. If not, the switch is bad and must be replaced.
Clean out any remaining debris left behind by the old stopper from the hole that the stopper goes into.
Press the new stopper into the hole on the metal plate until it snaps into place.
Shine the flashlight on the stopper and check that it sits flush against the metal plate.
Press and release the brake pedal and ask your assistant if the brake lights are turning off and on.
Replace the stoplight switch if the lights continue to stay on.
Loosen and remove the bolts holding the stoplight switch in place. It could be between one and four bolts depending on the vehicle.
Pull the stoplight switch from its mount. Disconnect the wiring harness from the stoplight switch by pressing or pulling the locking tab and puling the harness away from the switch.
Plug the wiring harness into the new switch until the locking tab clicks into place.
Place the new switch on the mount the old switch was removed from and tighten the bolts with a ratchet and socket.
Press and release the brake pedal several times and have your assistant check for proper operation.
