RAM 1500 Van V8-5.2L VIN Y (1999)
Brake Proportioning/Combination Valve: Testing and Inspection
Combination Valve Testing
METERING VALVE
The metering valve is used to balance brake action between the front disc and rear drum brakes. The valve holds off the initial pressure to the front
disc brakes until the rear brake shoes retracting springs are overcome. The valve is designed to maintain front brake fluid pressure at 241-517 kPa
(35-75 psi) until the hold-off limit of 310-689 kPa (100 psi) is reached. At this point, the metering valve opens completely permitting full fluid apply
pressure to the front disc brakes. This reduces front brake lining wear during low deceleration stops.
PRESSURE DIFFERENTIAL SWITCH
1. Have helper sit in drivers seat to apply brake pedal and observe red brake warning light.
2. Raise vehicle on hoist.
3. Connect bleed hose to a rear wheel cylinder and immerse hose end in container partially filled with brake fluid.
4. Have helper press and hold brake pedal to floor and observe warning light.
a. If warning light illuminates, switch is operating correctly.
b. If light fails to illuminate, check circuit fuse, bulb, and wiring. The parking brake switch can be used to aid in identifying whether or not the
brake light bulb and fuse is functional. Repair or replace parts as necessary and test differential pressure switch operation again.
5. If warning light still does not illuminate, switch is faulty. Replace combination valve assembly, bleed brake system and verify proper switch and
valve operation.