Stop light switch: common defects and their signs

1. Melting or oxidation of terminals.
   • Stop light lamps don’t turn on.
   • The ABS turns off at braking.
   • Most indicators on the instrument panel may light up at brake pedal pressing.
2. Damage of the switch wiring.
   • Stop signals are constantly on.
   • Indicators of the ESP (electronic stability program) and BAS (brake assist system) failure light up on the instrument panel.
   • Only one stop signal is on.

How to replace stop light switch?

The stop light limit switch is not restorable, so this component is to be replaced in case of breakdown.

Replacement algorithm for the cars of different models vary in accordance with the type of the switch and its fastening. If the switch is fixed to the brake pedal unit with the help of the lock washer and the clamp nut, the replacement procedure will be rather laborious.

There exists a type of the limit switches which are fastened with the help of retaining clips. It is a bit easier to perform replacement of such a component. For this you need to disconnect the battery negative terminal, remove the switch harness connector, and extract the component from its mounting seat after releasing the clip. Then a new switch is installed by pressing the retainers, or by rotating the component clockwise until it is locked in place by clips, according to the design. After installation, wires are connected to the switch, and you should check if stop signals activate during brake pedal moving within its free travel.

As in some cases access to the stop light switch can be difficult, unassisted replacement of the component is not recommended. If you don’t have such experience and equipment, then entrust works to service station professionals.