Expansion Valve Malfunction

Expansion Valve Malfunction

The valve stuck closed.

Complaint.

Cooling is not adequate.

Condition.

1. The low gauge reading is too low (0 or a vacuum).
2. The high side gauge reading is too low.
3. The discharge air from the evaporator only slightly cool.
4. The expansion valve shows signs of heavy sweating or frost.

Diagnosis.

The expansion valve restricting the refrigerant flow.

Correction.

1. Depressurise the system.
2. Renew the expansion valve.
3. Renew the drier bottle.
4. Evacuate the system using a vacuum pump.
5. Recharge the system with new refrigerant.
6. Operate the system and check the performance.

Restriction in the High Pressure Side.

Complaint.

Cooling is not adequate.

Condition.

1. The low side gauge reading is low.
2. The high side gauge reading builds up to an excessively high reading.
3. The discharge air only slightly cool.
4. The high pressure liquid hose from the drier bottle to the evaporator is cool to the touch or shows signs of heavy sweating or frost.

Diagnosis.

A restriction in the receiver-drier or the high pressure liquid hose from the drier bottle. Which results in the compressor removing refrigerant from the evaporator faster than it can enter. This results in a starved evaporator.

Correction.

1. Depressurise the system.
2. Renew the drier bottle and/or the high pressure liquid hoses or other defective parts.
3. Evacuate the system using a vacuum pump.
4. Recharge the system with new refrigerant.
5. Operate the system and check the performance.