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Home >> Jaguar >> 1982 >> XJ-6 L6-4.2L >> Repair and Diagnosis >> Brakes and Traction Control >> Hydraulic System >> Brake Proportioning/Combination Valve >> Testing and Inspection
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Brake Proportioning/Combination Valve: Testing and Inspection

Pressure Differential Warning Actuator

NOTE: Overhaul of the P.D.W.A. Unit is not possible, and the following test should be carried out at intervals detailed in the Maintenance Summary.

Before commencing procedures, be sure that car is adequately chocked and cars with automatic transmission have selector lever in 'P or 'N position.

OPERATIONAL CHECK
1. Be sure car is adequately chocked.
2. Check brake fluid level and top-up if necessary.
3. On cars with automatic transmission be sure gear selector lever is in 'N' neutral or 'P' (Park).
4. Check that with ignition on and handbrake applied 'Park Brake Warning' light is illuminated.
5. Run engine at idle speed and release handbrake.
6. Apply heavy foot pressure to brake pedal.

NOTE: The brake pedal should be fully depressed and kept fully applied throughout the following operations.

7. Release any brake caliper bleed nipple just sufficiently to allow fluid to be expelled, and be sure ejected fluid is collected in a jar or waste rag. Brake Warning light should illuminate.
8. Close bleed nipple.
9. Release and re-apply foot pressure to brake pedal.
10. Brake Warning light should extinguish.
11. Switch off engine and apply handbrake.
12. Top-up brake fluid reservoir. Should warning light fail to illuminate when fluid is released, repeat test operations.
13. A new P.D.W.A. unit is required if warning light fails to illuminate during repeat operation.

CHECK AND RESET
1. Release handbrake. Warning light should go out. If light remains illuminated, check brake reservoir fluid level. Top up as necessary. If warning light remains illuminated, carry out remaining operation.

2. Disconnect electrical connector from P.D.W.A. switch. If warning light goes out, P.D.W.A. has operated; if light remains illuminated check for short in brake warning electrical circuit or a sticking reservoir fluid level switch.

NOTE: If P.D.W.A. unit has operated a major defect in the brake system is indicated.

RESET
1. Resetting of the P.D.W.A. unit is achieved automatically during bleeding of the brake system, which should only be carried out following rectification of defects that caused shuttle valve displacement.
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