Combination Valve: Notes
Combination valve is used on all disc brake equipped cars. Valve combines functions of front brake hold-off (metering) valve, rear brake proportioning valve, and hydraulic pressure differential switch. Valve is mounted on left front frame side-rail and is connected to master cylinder and wheel cylinders through hydraulic lines. Wiring harness connects electrical terminal of pressure differential warning switch to brake warning light on instrument panel. Hold-off section limits pressure to front disc brakes until rear drum brakes are activated. Proportioning section supplies outlet pressure to rear brakes after a predetermined input pressure has been reached. This prevents rear wheel lock-up on vehicles with light rear wheel loads. Certain models having heavy rear wheel loads do not have proportioning feature. This section also has by-pass feature which is designed to assure full rear system pressure in event of front brake failure. Pressure differential warning switch is designed to constantly compare front and rear system pressure. In event of failure of either system, warning light will come on and remain on until proper repair is made and pressure is applied to pedal (to develope 450 psi line pressure).