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Proportioning Valve

  1. Rear wheel lock-up or skidding indicates a faulty proportioning valve. See Fig 1. Refer to the appropriate PROPORTIONING VALVE IDENTIFICATION  table. Road test vehicle to determine which rear brake system is faulty.
  2. If right rear wheel skids first under hard braking condition, install pressure gauge and "T" fitting of Tester Set (C-4007-A) in line between master cylinder secondary inlet brake line and control valve inlet. See Fig 2. Install second pressure gauge to right rear control valve outlet. Go to step 4).
    Fig 1: Identifying Proportioning Valve
    G91A11007Courtesy of CHRYSLER MOTORS.
  3. If left rear wheel skids first, install pressure gauges on opposite side of control valve. See Fig 3. Go to step 4).
  4. Bleed hoses and gauges. Have an assistant depress and hold pressure on brake pedal. Note and record pressure gauge readings. If inlet or outlet pressure readings DO NOT  agree with specifications, replace control valve. See BRAKE PRESSURE table.
Fig 2: Connecting Gauges for Right Rear Skid Test
G90H00825Courtesy of CHRYSLER MOTORS.
Fig 3: Connecting Gauges for Left Rear Skid Test
G90I00826Courtesy of CHRYSLER MOTORS.
BRAKE PRESSURE

Master Cylinder Pressure Split/Slope (1) Outlet Pressure Rear Brake
1000 psi 400 psi/.43 % 600-700 psi
1000 psi 400 psi/.27 % 525-600 psi
1000 psi 500 psi/.43 % 640-720 psi
1000 psi 600 psi/.43 % 685-755 psi
1000 psi 750 psi/.43 % 725-805 psi
1000 psi 800 psi/.45 % 765-845 psi
1000 psi 800 psi/.59 % 725-850 psi
(1) Split point is when proportioning valve changes rear brake pressure to prevent skidding. Slope is the pressure differential (percentage ratio) between front and rear brakes.
PROPORTIONING VALVE IDENTIFICATION (NON-ABS)

Body Application Split/Slope (1) Color
AA 14" Wheel Disc/Drum 400 psi/.43 % YEL
AA 14" Wheel Disc/Disc 400 psi/.27 % WHT
AP 14" Wheel Disc/Drum 400 psi/.43 % YEL
AP 14" Wheel Disc/Disc 400 psi/.43 % YEL
AY 14" Wheel Disc/Drum 500 psi/.59 % BLK
AG 14" Wheel Disc/Drum 400 psi/.43 % YEL
AG 15" Wheel Disc/Disc 400 psi/.27 % WHT
AJ 14" Wheel Disc/Drum 400 psi/.43 % YEL
AJ 14" Wheel Disc/Disc 500 psi/.27 % GRY
AJ 15" Wheel Disc/Disc 400 psi/.43 % YEL
(1) Split point is when proportioning valve changes rear brake pressure to prevent skidding. Slope is the pressure differential (percentage ratio) between front and rear brakes.
PROPORTIONING VALVE IDENTIFICATION (ABS)

Body Application Split/Slope (1) Color/Code (2)
AA 14" Disc/Disc 290 psi/.45 % BLK 20/.5
AA 15" Disc/Disc 430 psi/.45 % BLK 30/.5
AC 14" Disc/Drum 290 psi/.30 % BLK 20/.3
AY 14" Disc/Disc 290 psi/.30 % BLK 20/.3
AG 15" Disc/Disc 435 psi/.45 % BLK 30/.5
AJ 15" Disc/Disc 435 psi/.45 % BLK 30/.5
(1) Split point is when proportioning valve changes rear brake pressure to prevent skidding. Slope is the pressure differential (percentage ratio) between front and rear brakes.
(2) See Fig 1.
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