Brake Lamp Switch: Operation

WARNING: This page is about a different car, the 2004 Dodge Intrepid, 2004 Chrysler Intrepid, 2004 Chrysler Concorde, and 2004 Chrysler 300M. However, it is still accessible from the selected car via links, so may be relevant.

The brake lamp switch has three internal switches used for various functions. Among these are:

Brake lamp actuation
Speed control deactivation, and
Brake sense for ABS and brake transmission shift interlock

When the brake pedal is in the released position, the plunger on the outside of the brake lamp switch is pushed inward by the brake pedal. In this position, the electrical contacts for one internal switch are open while the electrical contacts for other two internal switches are closed.

When the brake pedal is pressed, the plunger on the outside of the brake lamp switch extends outward. This action closes the electrical contacts for the one internal switch and opens the contacts for the remaining two switches within the brake lamp switch. The internal switch which closes when the brake pedal is pressed completes the circuit to the brake lamps at the rear of the vehicle, thus allowing illumination of the brake lamps and the center-high-mounted stop lamp (CHMSL).