Brake Warning Indicator: Description and Operation

CIRCUIT OPERATION
The Brake Warning Indicator lamp is used to alert the operator of a problem with the vehicles braking system. The lamp illuminates when the ignition switch is turned to the START position to perform a self check.

There are two switches used in this system and they are wired in parallel form. A parking brake switch located on the parking brake mechanism will illuminate the lamp if the normally OPEN switch is CLOSED.

The other switch used is the brake warning lamp switch. This switch is normally OPEN. When the brake system pressure is below a predetermined level the switch CLOSES and completes a path to ground from the G99 circuit at the message center, through the switch.

Power for the lamp is supplied on circuit G5. This circuit is protected by a 5 Amp fuse located in cavity 8 of the fuse block and is HOT in the START and RUN position only Power for the fuse is supplied on circuit A21 from the ignition switch.

Power for the A21 circuit is supplied on circuit A1. This circuit is protected by a fusible link located near the auxiliary jumper post on the left toe box.