Compressors: Scroll, Reciprocating, Rotary & Semi-Hermetic

The most common signs are a compressor that hums but won't start, one that trips its breaker repeatedly, or a system that runs but produces little to no cooling. Start by checking for obvious issues first, like a tripped breaker, a failed capacitor, or a stuck contactor, since these are cheaper fixes that can mimic compressor failure. If the compressor hums without starting and a capacitor swap doesn't resolve it, or if it's drawing locked-rotor amperage without turning, that points to an internal mechanical or electrical failure inside the compressor itself. A licensed HVAC technician can confirm compressor failure with an ohmmeter test on the windings and a check of refrigerant pressures, which rules out other causes like a refrigerant leak or a failing fan motor.

Compressor replacement involves recovering refrigerant, brazing connections, evacuating the system, and recharging refrigerant, all of which require EPA Section 608 certification by law. Beyond the legal requirement, an improperly evacuated system or contaminated refrigerant charge can cause the new compressor to fail prematurely, so this job is best left to a licensed HVAC technician even for buyers comfortable with other DIY repairs.

A hermetic compressor is fully sealed and cannot be opened for internal repair, so it's replaced as a complete unit when it fails. A semi-hermetic compressor has a bolted housing that allows a technician to access and repair internal components like valves and bearings.

Crankcase heaters are recommended for compressors that sit in cold ambient conditions during off-cycles, since they prevent liquid refrigerant from migrating into the crankcase and diluting the oil. Many commercial and outdoor installations include one as standard equipment; check your original compressor's specifications to see if one was fitted.

Compressors on this page are built for specific refrigerants, most commonly R-410A, R-404A, R-22, and R-134a. Always match the replacement compressor's refrigerant to what's already in your system rather than converting refrigerants without a full system retrofit.

Most compressors last 10 to 15 years under normal operating conditions, though this varies with usage, maintenance, and electrical supply quality. Frequent short-cycling, low refrigerant charge, and electrical issues can significantly shorten a compressor's lifespan.