Brake Lamp: Description and Operation

Brake Lights


Battery voltage is supplied at all times through fuse 39 to the brake switch. When you push the brake pedal, the brake switch contacts close, supplying battery voltage through the coils of the left and right brake failure sensors to the brake lights and to the high mount brake light. The brake lights are grounded at G451. The high mount brake light is grounded at G252.


Safety Indicator


When you turn the ignition switch to RUN, voltage is applied to the safety indicator circuit which provides ground for the "brake lamp" indicator for a few seconds. The indicator comes on for those few seconds to test the bulb.


With the brakes off, ground is provided for the safety indicator through either of the failure sensor coils and any of the brake light bulbs.


When you push the brake pedal, battery voltage is applied to all the failure sensor coils. The coils close the relay contacts, and the safety indicator circuit WHT/GRN wire stays grounded. If one of the brake light bulbs fails, at least one of the failure sensor coils will not be energized. The safety indicator circuit WHT/GRN wire will then not be grounded by either the diode or the relay contact, which will cause the safety indicator circuit to turn on the "brake lamp" indicator.