A compressor is the mechanical unit of an outdoor air conditioner or heat pump that compresses and pumps refrigerant gas to cool your house.
The compressor in the air conditioner or heat pump circulates refrigerant. It heats up the refrigerant into a gas then pumps it into the condensing coil where it loses heat and condenses (turns into a liquid) to cool your home.
Compressors can work at either a single level of operation or two stages. A single-stage cooling system means your air conditioner or heat pump has only one level of cold output. Two-stage cooling means the air conditioner or heat pump has a compressor with two levels of operation: high for hot summer days and low for milder days. Since the low setting is adequate to meet household cooling demands 80% of the time, a two-stage unit runs for longer periods and produces more even temperatures.
Longer cooling cycles also translate to quieter, more efficient operation and enhanced humidity control. Compared to a single-stage unit, a two-stage air conditioner or heat pump can remove twice as much moisture from the air. This is important because when moisture levels are high, there’s a higher potential for mold and other pollutant problems.
Various problems with the compressor can occur. Dust, dirt and grime can build up on the condenser coil causing inefficient heat expulsion which forces your system to work harder to cool your home. Refrigerant lines can become blocked or damaged, or develop holes or cracks causing it the refrigerant to leak out. All of these issues result in the compressor having to work too hard. The increased pressure and temperature can cause the compressor to overheat and fail. Other issues like electrical problems and inadequate oil lubricant can cause compressor failure as well.
If your compressor has already failed or is failing, your only options are to get a new one or completely replace your air conditioning system. A compressor is very expensive so many people opt to just get a new system especially if the unit is still using R-22 refrigerant as R-22 refrigerant is being phased out.