Troubleshooting

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When working with compressed air wear safety glasses and protective clothing.

PROBLEM: Low air pressure.

POSSIBLE CAUSES:

1. Broken spring on compressor inlet valve.

2. Compressor unloader plungers sticking, thus holding inlet valves off their seats.

3. Governor set too low.

4. Air dryer check valve leaking.

5. Safety valve leaking or blowing off too early.

6. Reservoir drain tap leaking.

7. Leaking hoses/valves/actuators.

PROBLEM: High air pressure (safety valve may blow off).

POSSIBLE CAUSES:

1. Governor set too high.

2. Compressor cut-out mechanism faulty.

PROBLEM: Inter-axle differential lock clutch fails to disengage.

POSSIBLE CAUSES:

1. Actuating cylinder damaged.

2. Low Air Pressure.

PROBLEM: Inter-axle differential lock clutch fails to engage.

POSSIBLE CAUSES:

1. Differential lock valve leaking air to the actuating cylinder.

2. Actuator cylinder damaged.

PROBLEM: Brake failure (service brake).

POSSIBLE CAUSES:

1. Diaphragm in service chamber of spring brake actuator ruptured.

2. Dual brake valve fault.

3. Quick release valve not passing air.

PROBLEM: Brake failure (parking brake).

POSSIBLE CAUSES:

1. Relay valve failing to exhaust air from the inlet side of the quick release valve.

2. Actuator power spring broken.

3. Actuator piston sticking.

4. Relay valve stuck closed.

5. Pilot pressure holding relay valve open due to faulty parking brake valve.

PROBLEM: Service/Parking brakes inefficient.

POSSIBLE CAUSES:

1. Brake linings worn.

2. Brakes out of adjustment (automatic adjusters may be damaged or seized).

Governor

The governor cut-out pressure can be adjusted if necessary:-

1. Install an accurate pressure guage (0-1000 kPa/0-150 p.s.i.) in test port (4).

2. Start the engine and allow the system to charge up to governor cut-out pressure. The compressor has cut-out when the reading on the pressure gauge stops rising.

3. If necessary, adjust the cut-out pressure by slackening the locknut (3) and turning adjusting screw (2). Turn counter-clockwise to increase the cut-out pressure. The correct value is given in "specifications". After turning the screw clockwise (to reduce the cut-out pressure) it will be necessary to exhaust air from the system until the compressor cuts in and re-charges the system to the new cut-out pressure.

Ensure that the adjusting screw is locked in place and replace the rubber cover (1).

Governor

1. Rubber Cover

2. Adjusting Screw

3. Locknut

4. Test Port

Govenor

4. With the system charged to the correct cut-out pressure slowly lower the pressure until the compressor cuts in and note the reading. The compressor has cut-in when the pressure reading on the gauge starts to rise again.

5. If the cut-out/cut-in pressure readings are not within the values given in "specifications" after adjustment the governor must be disassembled and overhauled or replaced.

System Protection Valve

Pressure Setting.

1. Install an accurate pressure gauge (0-1000kPa/0-150 p.s.i.) in the governor test port.

2. Remove the outlet pipe from any one element in the system protection valve.

System Protection Valve

3. Start the engine and operate at low idle.

4. Note the reading on the pressure gauge when air begins to flow from the disconnected port.

5. If the setting is incorrect, stop the engine, remove the rubber gaiter from the relevant element and turn the adjusting screw to vary the setting. Turn clockwise to increase the setting.

6. Exhaust pressure from the air dryer (crack the inlet pipe), restart the engine, repeat the test until the setting is correct.

7. Repeat steps 2 to 6 for each element in turn.

8. Remove the test gauge and replace and tighten all fittings.

Wheel Brake Adjustment

The wheel brakes are self adjusting during normal operation and should maintain the correct clearances between the linings and drums until the linings are replaced. An initial adjustment is required when the linings are replaced or if the brake assembly has been disassembled for any reason.

The brake linings should be checked for wear every 250 service meter hours and replaced when they are worn to 8 mm thickness.

Initial Adjustment

1. Remove both dust covers from the wheel brake.

Brake Linings

2. Turn the adjusting screw (1) until the brake lining is in contact with the drum (2). DO NOT FORCE THE ADJUSTING SCREW.

Adjusting Screw

3. Turn the adjusting screw (1) in the opposite direction until the clearance between the lining and drum (measured at the centre of the lining) is 2 mm maximum. This should take about eight notches or clicks of the adjuster.

4. Repeat steps 2 and 3 using the other adjusting screw to set the clearance between the other brake lining and drum.

5. Install the dust covers.

6. Repeat the entire procedure for the other wheel brakes in turn.

Brake Cylinder Assembly Adjustment

If the brake cylinder assembly has been replaced for any reason it will be necessary to carry out the following adjustment to ensure correct installation. Carry out the procedure before installing the brake actuator.

1. Check the position of the wedge assembly (2) to be sure the rollers (10) are correctly positioned against the plunger assemblies (1).

2. Apply 9S3263 threadlock to the threads of the tube (8) - countersunk end, and screw the tube fully into the brake cylinder assembly (9).

3. Install the follower assembly (3).

4. Connect the air lines to the brake actuator (6).

5. Start the engine and allow the system pressure to increase to normal. Move the parking brake control valve lever to the OFF position to fully retract the actuator pushrod (5). Place the actuator in position against the end of tube (8) so that pushrod (5) fits into follower (3).

Cylinder Assembly

6. Measure the clearance (A) between the face of the actuator and the end of the tube.

Tube Assembly

7. Remove the actuator (6).

8. Apply 9S3263 threadlock to the threads of the tube (8) and screw flange (4) on until the flange face is clear of the tube end by the clearance (A) measured in step 5. The mounting holes in the flange must be vertical. Back off the flange as required (up to one full turn) to obtain the vertical alignment.

9. Lock the flange (4) in position using set screw (7).

10. Install the brake actuator.