Brake Warning Indicator: Description and Operation

The red BRAKE warning lamp is located in the instrument panel cluster and is used to indicate a low brake fluid condition or that the park brakes are applied. In addition, the brake warning lamp is turned on as a bulb check by the ignition switch when the ignition switch is placed in the crank position. Problems with this system will generally be of the type where the warning lamp fails to turn on when it should, or remains on when it should not.

The warning lamp bulb is supplied a 12 volt ignition feed anytime the ignition switch is ON. The bulb is then illuminated by completing the ground circuit either through the park brake switch, the fluid level sensor in the master cylinder reservoir, the ignition switch in the crank position.

Master Cylinder Fluid Level Sensor:

The Brake Fluid Level sensor is located in the brake fluid reservoir of the master cylinder assembly. The purpose of the sensor is to provide the driver with an early warning that brake fluid level in master cylinder reservoir has dropped to below normal. This may indicate an abnormal loss of brake fluid in the master cylinder fluid reservoir resulting from a leak in the hydraulic system.

As the fluid drops below the minimum level, the fluid level sensor closes the brake warning light circuit. This will turn on the red brake warning light. At this time, master cylinder fluid reservoir should be checked and filled to the full mark with DOT 3 brake fluid. If brake fluid level has dropped in master cylinder fluid reservoir, the entire brake hydraulic system should be checked for evidence of a leak.