Heat-pump reversing valve changes refrigerant direction between heating and cooling. Related symptoms include heats in cooling, cools in heating or will not change modes. Those symptoms do not prove the component failed: prove thermostat configuration, outdoor operation and mode behavior.
What this covers
- air-source heat pumps
What it does not cover
Differential
Likely causes of “Heat-pump reversing valve”, and how to tell them apart
- 1
The thermostat's heat-pump configuration is wrong
What separates it The system heats in cooling mode or cools in heating mode from the first day or after a thermostat swap.
How to confirm Check the thermostat's equipment type and the O/B setting against the installer's record.
- 2
The O/B wire is connected or labeled incorrectly
What separates it The problem began after a wiring change, and the wire labels do not match the installation record.
How to confirm Compare the wire labels with the photograph taken before the change.
- 3
The system is in defrost or auxiliary heat
What separates it Cool air blows for a few minutes in winter while the outdoor unit runs in defrost, then it recovers.
How to confirm Check whether the change lasts a few minutes at cold temperatures and then corrects itself.
- 4
The valve is stuck or has failed
What separates it The settings and wiring are right and the unit still stays in one mode or will not change, or the outdoor unit makes a hissing sound when switching.
How to confirm This needs a technician to test the coil and the valve; it is sealed refrigerant work.
Before you touch a setting
Record this first — changing settings destroys the evidence
- The thermostat mode, the equipment type setting and the wire labels with a photograph.
- Whether the wrong mode is constant or appears only at certain temperatures.
- Whether the outdoor unit and the indoor air behave opposite to the setting.
Try in this order
0 of 2 completedTest before you replace
ReversibleProve thermostat configuration, outdoor operation and mode behavior.
Weigh the repair
ReversibleReplacement difficulty for the heat-pump reversing valve is professional refrigerant/electrical diagnosis.
Stop boundary
When this stops being a self-service repair
- !Turn the system off rather than testing repeatedly; running the wrong mode can overheat the house or stress the compressor.
- !Replacement involves refrigerant and brazing and belongs to a licensed technician.
Evidence ledger
Sources behind this answer
Exact questions
Common questions
What does a reversing valve do?+
It changes the direction that refrigerant flows so the same outdoor unit can heat or cool the house.
How can I tell whether the valve is stuck or the thermostat is wrong?+
Change the thermostat between heat and cool and listen for a click at the outdoor unit. If the air stays the same and the thermostat's O or B setting matches the equipment, the valve or its solenoid may be at fault, which a technician can test.
Does a hissing sound mean the valve is failing?+
A short whoosh when the unit changes mode is normal. A steady hiss while running, with poor heating or cooling, can mean the valve is passing refrigerant and needs a technician.
Can I keep running the heat pump with a stuck valve?+
It is better not to. It may blow cool air in winter or warm air in summer, which wastes energy and stresses the compressor. Use another heat source and call a technician.
Why does my heat pump heat in cooling mode?+
Often the thermostat's reversing valve setting is the opposite of what the unit needs, or the wires are connected to the wrong terminals. Check the setting and wiring before assuming the valve has failed.
How can I tell it is stuck?+
The unit heats in cooling mode or cools in heating mode. A technician confirms it.
Is this a homeowner repair?+
No. It involves refrigerant and needs a licensed technician.