Plain-language explanation: This page is educational and does not replace testing the actual equipment.
What the reversing valve does
It redirects high-pressure refrigerant to determine which coil acts as the condenser and which acts as the evaporator.
Common symptoms
The unit may be stuck in heating or cooling, fail to change modes, produce abnormal pressures, or make unusual hissing sounds.
Electrical versus mechanical problems
A failed solenoid coil, missing control voltage, wiring problem, pressure imbalance, or stuck internal slide can create similar symptoms.
Why diagnosis matters
A reversing-valve replacement is a significant refrigeration repair, so control and pressure conditions should be confirmed first.
Frequently asked questions
Can a thermostat cause the same symptom?
Yes. Thermostat configuration, wiring, or control-board problems can prevent the valve from being commanded correctly.
Can the valve be repaired without replacement?
Sometimes the problem is the solenoid coil or controls. A mechanically failed valve usually requires replacement.
Is hissing always a bad valve?
No. Refrigerant movement can create normal sounds, but unusual or continuous hissing should be evaluated.