Compressor
The pump at the centre of the refrigeration circuit. It raises the pressure and temperature of refrigerant vapour so heat can be rejected at the condenser. Protection codes exist to stop the compressor before pressure, current, or temperature moves outside its design range.
Also called compressor motor
What does a compressor do?
The compressor is the pump that drives a refrigeration circuit. It raises refrigerant vapour to a high pressure and temperature so the heat it carries can be released at the condenser coil.
Compressor: how it works
Low-pressure vapour leaves the evaporator carrying the heat it absorbed, and the compressor squeezes it into a smaller volume. That raises its temperature above the outdoor air, which is the only reason the heat will flow out of it at the condenser. Everything else in the circuit exists to keep the compressor fed with vapour rather than liquid.
Where you meet the term
- In a protection code, where the board stopped the compressor because a limit was reached rather than because the compressor failed.
- In a quotation, where compressor replacement approaches the cost of the outdoor unit and the age of the system becomes the decision.
- In a noise complaint, where a change in the sound at start-up is the observation a technician wants described.
How to check it
- Note whether the outdoor fan runs without the compressor. A fan turning while the unit produces no cooling narrows the search to the compressor circuit rather than to the whole outdoor supply. Owner check
- Record the code and the conditions it appeared under. Outdoor temperature, how long the system had run, and whether it had just restarted all change what a protection code points at. Owner check
- Measure running current against the data plate. The plate states rated load amps. A reading well outside it, taken with the correct instrument on a live circuit, is technician work. Technician
Compressor: what it is not
- A compressor protection code does not mean the compressor has failed. It records that a limit was reached, and clearing it without finding the cause repeats the event.
- Compressors do not consume refrigerant. A circuit low on charge has lost it somewhere, and topping up without finding the loss is a temporary measure.
Compressor questions
Why does the compressor stop but the fan keeps running?
Boards can keep the fan running after stopping the compressor, either to cool the outdoor coil or as part of a protection routine. It tells you power reaches the unit and the control board is still awake.
How long should a compressor last?
Life depends on the run conditions it has been kept in rather than on hours alone. Repeated protection events, low charge, and restricted airflow all shorten it, which is why the cause behind a code matters more than the code.
Can I test the compressor myself?
No. Testing means opening a live electrical compartment that also holds charged capacitors, and any refrigerant-side measurement requires certification. Observing symptoms and recording codes is the owner-side limit.
Where this definition comes from
Written from manufacturer support article material held in the HVAC Bench evidence record. Where a document limits a definition to certain models, that limit is repeated here rather than generalised across a brand.
- Mini-Split Compressor Not Turning OnTrane ductless outdoor operation, breaker stop points, airflow observations, and compressor service limits.
- GREE H5 Error Code: IPM Protection Causes and Fix GuideGree residential systems covered by the manufacturer technical article.