The compressor is one of the most important components in any split air conditioning system. The compressor functions as the split system's 'heart', keeping refrigerant fluids flowing from the outdoor unit to the indoor unit(s) and vice versa.

A split system's compressor also has something else in common with a heart -- when it stops working properly, so does everything else. Compressors can fail for a variety of reasons, but fortunately, they can usually be repaired or replaced relatively quickly by a professional residential HVAC service company. Here are three of the most common causes of split system compressor failure:

Insufficient Or Contaminated Lubricant

All types of split system compressors, including pistons, screws, and scroll-type compressors, must be properly lubricated to function efficiently. If lubricant levels in your system are too low, the compressor will create excess friction while functioning, causing it to overheat. Overheating can also occur if the lubricant has been contaminated by water or other substances, which can reduce the lubricant's anti-friction properties. 

Overheating can quickly cause catastrophic damage to any compressor, so you should make sure your system's lubricant levels are inspected and topped off regularly by HVAC service professionals. If the lubricant has become contaminated, you should also have the compressor and lubricant reservoir inspected for damage.

Refrigerant Line Blockages

Refrigerant lines are narrow pipes that connect the split system's indoor and outdoor units. The system's compressor forces the fluids through these pipes, providing cooled fluids to the indoor units, and drawing fluid back to the outdoor unit once they have been used.

If one or more of these refrigerant lines become blocked by debris, fluid pressure levels inside the lines can increase rapidly, causing fluid to back up into the compressor. This can place the compressor under extreme stress and is particularly damaging to the compressor's motor, which has to work even harder as pressure builds up inside the system.

Most split systems have compressors with automatic cut-off switches, which deactivate the system when internal pressures are too high. If your system's compressor shuts off a few seconds or minutes after the system activates, a refrigerant line blockage is likely to blame, although you should call in a professional HVAC repair service to conclusively diagnose the problem.

Blockages in refrigerant lines can usually be removed quickly by a professional repair service, getting your split system back up and running. However, debris getting into the lines in the first place could be a sign that your refrigerant lines are cracked or leaking. If a blockage occurs, you should have the refrigerant line pipes inspected for damage and replaced if necessary, once the blockage has been removed.

Electrical Issues

The compressor produces most of the noise generated by a split system's outdoor unit, so if your outdoor unit is unusually silent, chances are the compressor isn't working. If you hear a low humming noise instead of usual operating noises, it is likely that the outdoor unit's condenser is functioning but the compressor is not. This problem is usually caused by electrical faults, such as damaged wiring, faulty starter relays, or malfunctioning capacitors. These parts can be replaced easily by a professional HVAC repair service.

Electrical faults are particularly common in older split systems and will become more common over time as parts wear out and wiring overheats. If your system is suffering from frequent electrical faults, replacing your system may be more economical than repairing it. 

For more information, contact a residential HVAC service near you to learn more.