DIRECT SUPPORT TROUBLESHOOTING PROCEDURES - continued

TM 9-4120-430-14

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FAULT PROCEDURE 7.

COMPRESSOR RUNS BUT DOES NOT COOL - Continued

MALFUNCTION

TEST OR INSPECTION

CORRECTIVE ACTION

COMPRESSOR RUNS BUT DOES NOT COOL

Step 6.

Check for high discharge pressure. (Refer to Table 1, WP 0050 00.)

Bleed off excess refrigerant.

Step 7.

Check operation of liquid solenoid valve. Unit may be in standby operation.

Check continuity of solenoid coil. Replace defective coil. Cycle equipment several times.

Perform refrigeration system pressure testing for low or expected discharge pressure. Refer to

WP 0050 00 for pressure testing.

FAULT PROCEDURE 8.

COMPRESSOR EXCESSIVELY NOISY

MALFUNCTION

TEST OR INSPECTION

CORRECTIVE ACTION

COMPRESSOR EXCESSIVELY NOISY

Step 1.

Listen for knocking.

Check for low suction line temperature indicating that liquid refrigerant is returning to

compressor. (Refer to WP 0050 00 and Table 1, WP 0050 00.)

Step 2.

Check for high discharge pressure indicating overcharge of refrigerant. (Refer to WP 0055 00 and

Bleed off excess refrigerant. Check HIGH pressure switch.

Step 3.

Check three phase power sequence, must be A-B-C for proper compressor rotation.

Refer to schematic diagram (WP 0038 00) for proper connections.

FAULT PROCEDURE 9.

SUCTION PRESSURE TOO LOW

MALFUNCTION

TEST OR INSPECTION

CORRECTIVE ACTION

SUCTION PRESSURE TOO LOW

Step 1.

Stop compressor and check expansion valve.

Remove remote bulb in suction line. Place bulb in ice water for 1-2 minutes. Start compressor.

Remove bulb from ice water and hold it in one hand to warm it. At the same time, check the

suction line for rapid change of temperature, which indicates flood-through of liquid refrigerant.

If liquid floods through valve, it is operating satisfactorily. If not, valve or remote bulb is faulty.

CAUTION

Do not let liquid flood back into compressor or compressor will be seriously damaged.

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