Durango 4WD V8-5.9L VIN Z (1998)
Brake Proportioning/Combination Valve: Description and Operation
GENERAL INFORMATION
The combination valve contains a pressure differential valve and switch and a proportioning valve. The combination valve/proportioning valve are
not repairable and must be replaced as an assembly.
PRESSURE DIFFERENTIAL SWITCH
The pressure differential switch is connected to the brake warning lamp. The switch is triggered by movement of the switch valve. The purpose of
the switch is to monitor fluid pressure in the separate front/rear brake hydraulic circuits.
A decrease or loss of fluid pressure in either hydraulic circuit will cause the switch valve to shuttle forward or rearward in response to the pressure
differential. Movement of the switch valve will push the switch plunger upward. This closes the switch internal contacts completing the electrical
circuit to the warning lamp. The switch valve may remain in an actuated position until repair restores system pressures to normal levels.
PROPORTIONING VALVE
The proportioning valve is used to balance front-rear brake action at high decelerations. The valve allows normal fluid pressure during moderate
braking. The valve only controls fluid pressure during high decelerations brake stops, when a percentage of rear weight is transferred to the front
wheels.
