The compressor is in the outdoor unit of your air conditioning system. Its job is to circulate the refrigerant. If your home still feels hot when the air conditioning is on, it may be a problem with the compressor. How do you know? Here are six common reasons why a compressor might fail.

1. Low refrigerant charge causes refrigerant vapor to overheat, which overheats the compressor, resulting in compressor motor winding degradation. Low refrigerant charge also slows down circulation of lubricating oil which makes friction surfaces hotter such as bearings and pistons.

2. Excessive refrigerant charge can result in flooding, or liquid refrigerant in the evaporator not evaporating entirely. Liquid refrigerant supplied to the compressor can flash to vapor causing the lubrication oil to boil and foam, potentially damaging the compressor. It can also lead to slugging, or larger amounts of liquid refrigerant entering the piston cylinders and causing additional stress and damage to the compressor, given that liquids resist compression much more than gases.

3. Refrigerant piping problems can include too small or too large diameters, internal scale formation or leaks. Refrigerant line length and diameter are crucial for proper compressor performance. During manufacturing, poor brazing can result in scale building inside the piping. This can flake off and circulate through the system, clogging filters, strainers and expansion valves.

4. Oversized capacity means the system meets the load too quickly, resulting in short cycling. The constant cycling wears out the compressor.

5. Poor airflow from dirty coils or a dirty filter. A dirty outdoor condenser coil will result in the inability to reject heat. A dirty indoor filter restricts air flow across the evaporator. Both conditions result in a hotter running compressor.

6. Electrical problems include bad start capacitors or fan failure. Compressor start capacitors give a voltage boost to compressor motors that are already loaded with pressurized refrigerant. Bad capacitors result in difficulty starting up, stuttering during start, and frequent shut off from overheating.

If you suspect a problem with your compressor, contact a qualified HVAC professional. Air conditioning compressors typically last for 10 to 20 years, depending on how and where they are used. If your system is older, consider upgrading to a new, ENERGY STAR®-certified air conditioner or heat pump. Beltrami Electric Cooperative has great rebates for air source and ground source heat pumps! Check them out here.