Brake Proportioning/Combination Valve: Testing and Inspection

Fig. 4 Height sensing proportioning valve assembly.:

Dakota models use a height sensing proportioning valve in addition to a pressure differential switch. When a premature rear wheel skid is obtained during braking, it may be an indication of an improperly adjusted proportioning valve, air in bypass line or a malfunction has occurred within the proportioning valve. First bleed and readjust valve. If problem is not resolved, proceed as follows to test valve assembly:
1. Remove actuator assembly adjustment nut, then the actuator arm assembly from valve lever.
2. Install one gauge and Tee from line pressure set No. C-4007-A or equivalent between brake line from combination valve to input port of proportioning valve.
3. Install second gauge from line pressure set No. C-4007-A or equivalent directly to valve output port. Bleed rear brake system including two bleeder screws on valve.
4. Have an assistant exert pressure on the brake pedal to obtain a pressure reading of 1000 psi on gauge to valve inlet port. Gauge on output port should read 225-325 psi. If not, replace valve and torque mounting bolts to 100 inch lbs.
5. If both gauges read correctly, reinstall actuator arm assembly, adjust, and bleed rear brakes and valve, then road test vehicle.