The combination valve has three sections:
| • | The metering section limits front disc brake pressure, allowing
just enough pressure to overcome the rear brake shoe springs. When the inlet
pressure is below 200 kPa (30 psi ), there is no restriction.
This allows for pressure equalization when the brakes are not applied. |
| • | The pressure differential warning switch constantly compares front
and rear brake pressures from the master cylinder. The switch activates the
BRAKE warning lamp when a malfunction occurs in the front or rear brake system.
The switch latches in the warning position after a malfunction occurs. To
turn off the lamp you must repair the malfunction and apply enough pedal pressure
in order to develop about 3100 kPa (450 psi ) brake
line pressure. |
| • | The proportioning section limits brake line pressure to the rear
brakes after a predetermined rear input brake line pressure is reached. This
prevents rear wheel lockup on vehicles with light rear wheel loads. |
The bypass feature on the combination valve ensures full system pressure
under the following conditions:
| • | Full system pressure to the rear brakes when there is a malfunction
in the front brake system. |
| • | Full system pressure to the front brakes when there is a malfunction
in the rear brake system. |
