300TE 4MATIC (124.290) L6-3.0L (103.985) (1991)
Brake Light Switch: Description and Operation
As in previous versions of cruise control, the cruise control circuit continuously monitors the ground signal from the brake lamp bulbs: The unlit lamps
are basically a low amperage signal ground. When the brake lamp switch is operated, the power to the bulbs lights them, raising their resistance and
electrically removing the ground. Thus, when the brake lamps come on the cruise control operation is interrupted, and the throttle valve position is once
again determined by the accelerator pedal position.
NOTE: If there is no ground signal through the brake lamps (e.g., bulbs are burned out or removed) the cruise control cannot function. Neither ASR nor
electronic accelerator control are affected.