Expansion Valve Malfunction

VALVE STUCK OPEN
Complaint--Little or no cooling.





Condition
- The low side gauge reading is too high.
- The high side gauge reading is normal or slightly low.
- The discharge air from the evaporator is warm.
- The suction hose and the evaporator show signs of heavy sweating.

Diagnosis--The expansion valve is allowing excessive flow of refrigerant through the evaporator coils causing flooding of the coils.

Correction
- Depressurize the system.
- Renew the expansion valve.
- Renew the dryer bottle.
- Evacuate the system using a vacuum pump.
- Recharge the system with new refrigerant.
- Operate the system and check the performance.

VALVE STUCK CLOSED
Complaint--Cooling is not adequate.





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

Diagnosis--The expansion valve is restricting the refrigerant flow.

Correction
- Depressurize the system.
- Renew the expansion valve.
- Renew the dryer bottle.
- Evacuate the system using a vacuum pump.
- Recharge the system with new refrigerant.
- Operate the system and check the performance.