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Compressor Overheating Troubleshooting | Air Conditioner Repair

What you will learn from Compressor Overheating Troubleshooting article:
1) Avoiding the problem of compressor overheating
2) how does compressor overheating effect the refrigeration system?
3) diagnosing compressor overheating
4) repairing the problem of compressor overheating and future prevention
5) lots of related links to help you learn

Compressor Overheating Troubleshooting | Air Conditioner Repair – There are some problems with air conditioner or heat pump compressors that can be avoided with proper maintenance. Other problems result in a mechanical or electrical problem with the systems that need to be resolved. Compressor overheating is an issue that can cause serious problems with your air conditioner or heat pump system.

A compressor that overheats can still operate and provide cooling or heating but if the temperature inside the compressor rises too high then the oil in the compressor can break down and reduce the lubrication and cooling effect the oil has inside the compressor for proper and necessary lubrication. This leads to possible mechanical failure and other problems that will occur to the compressor and in the refrigeration system that results from compressor overheating. When the oil becomes overheated it changes chemically. Through a lack of lubricating and cooling it becomes like an acid when the oil overheats. This eats away at the windings and will cause compressor failure.

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Compressor Overheating Troubleshooting | Air Conditioner Repair

The check for excessively high temperatures is to take a discharge temperature on the discharge line at least 6 inches from where it leaves the compressor. Temperatures over 300° Fahrenheit inside the discharge port of the compressor means there is a serious problem that needs to be addressed.

What are the causes of compressor overheating and how to fix it:

  • High Head Pressure - This can be caused by dirty condenser coils, a bad condenser fan motor, a recirculation of air back into the coils, improper rotation of the condenser fan, non-condensibles (air, nitrogen or other gas), and an overcharge of the refrigeration system. Another thing found that can cause this is any extra heat source near the condenser such as a drier vent which can introduce extra heat into the system.I have a customer who called me for a bid to install a new system. The customer received 3 different bids from 3 different contractors. My competition got the contract and installed the new split system air conditioner. The next summer I got a call from that same customer asking me to check out their air conditioner. It seems my competitor had installed the condenser under a deck and near many bushes. The condenser could not breathe and the air and heat was simply recirculated back into the unit. Once the recirculated heat rises about outdoor ambient temperature you lose effective cooling because the condenser was no longer rejecting the latent heat picked up in the evaporator, suction line, and the heat from compression. I moved the unit to a better location and the customer called me later and told me the difference was like night and day.It wasn’t difficult to figure out this problem for anyone and who knows why the competition chose that location but I used the experience to teach a few junior technicians about heat rejection and compressor overheating. I had them take temperatures and pressures and let them come to the conclusion of the main problem. Once the line was cut to move the unit I also had them test the oil to make sure it was acid-free. After all, when everything was said and done I did not want to have any warranty issues replacing a compressor because I did not do my homework.
  • Improper Voltage - This can be a power company issue that needs to be corrected by the power company especially high voltage but low-voltage can be a problem in the circuits providing power to the compressor. Lose connections and corroded wires or terminal connections can cause low voltage and high amperage problems that result in compressor overheating. This can also be the result of a power company transformer issue along with the high voltage problem.
  • High Superheat - this can result from a low refrigerant charge, a restriction in the refrigerant piping or a faulty metering device. It can also result in a liquid line too close to a heat source such as hot water piping loops. In that case the liquid line needs to be insulated from the hot water piping or relocated.
  • Short Cycling of Compressor - this can be caused by a low charge or faulty metering device. Air flow across the evaporator coil can also result in this issue and can be from a dirty or clogged air filter or frozen evaporator coil. A bad capacitor can also cause the problem.
  • Other Possible Causes - A failure of the internal overloads inside the compressor or bad compressor valves can cause issues with overheating. These problems can be difficult to resolve in hermetic compressors without replacing the compressor. Heat pumps with faulty reversing valves can also be an issue.
Related Link: Air Conditioner Sequence of Operation (opens in a new window)

Compressor Overheating Troubleshooting Additional Testing

Both hermetic and semi-hermetic compressors are difficult to troubleshoot sometimes and many times the problem is external to the compressor or a result of poor installation skills by the installation technician if the compressor was recently replaced or it is a split system where the system was evacuated by an HVAC technician. It is recommended when any type of refrigeration system is put into service that a refrigeration triple evacuation be performed to ensure all moisture is removed from the system. Moisture leads to bad windings in the compressor and can be a cause of overheating. The only real way to tell if the windings are healthy is to use a megaohmmeter or a megger to test the windings to make sure they are not damaged from moisture in the system. You can also test the refrigerant with a basic acid test available at most supply houses.

Compressor Overheating Troubleshooting Conclusion

It is important to resolve this matter as soon as possible to prevent further damage to the system. Some of the problems can easily be resolved while others will require major surgery. Happy compressor troubleshooting and good luck.

Do you have a heat pump instead of an air conditioner? See our comprehensive heat pump category for help with heat pumps:

Furthermore, additional heat pump resources here:

Compressor Overheating TroubleshootingHigh Performance HVAC Air Conditioning and Heating SystemsCompressor Overheating Troubleshooting | Air Conditioner Repair

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