The brake pressure indicator and distribution switch (found on 1967-77 vehicles) is connected to the hydraulic lines from the master cylinder and is a pressure differential type, designed to light the brake warning lamp on the instrument panel if either the front or rear hydraulic system fails. The brake warning light will come on only when the brakes are applied. It will not remain on when the brakes are released. This switch is a non-adjustable and non-serviceable component and must be replaced if found defective.
REMOVAL & INSTALLATION
See Figure 1
- Disconnect the negative battery cable.
- Disconnect the electrical lead from the switch assembly.
- Place dry rags below the switch to absorb any spilled fluid.
- Clean any dirt from the switch and hydraulic lines and disconnect the hydraulic lines at the switch. Cover the open line ends to protect the system from dirt.
- Remove the mounting screw and remove the switch.
- To install reverse the removal procedure and bleed the brake system.
TESTING AND CENTERING THE SWITCH
Whenever work on the brake system is done, it is possible that the brake warning light will come on and refuse to go off when the work is finished. In this event, the switch must be centered.
- Raise and support the vehicle.
- Attach a bleeder hose to the rear brake bleed screw and immerse the other end of the hose in a jar of clean brake fluid.
- Be sure that the master cylinder is full.
- Turn the ignition key ON. Open the bleed screw while an assistant applies heavy pressure on the brake pedal. The warning lamp should light. Close the bleed screw before the helper releases the pedal.
To reset the switch, apply heavy pressure to the pedal. This will apply hydraulic pressure to the switch which will recenter it.
- Repeat Step 4 for the front bleed screw.
- Turn the ignition OFF and lower the vehicle.
If the warning lamp does not light during Step 4, the switch is defective and must be replaced.