Signs & Symptoms of a Bad HVAC Compressor


An HVAC can have problems like any other appliance or equipment unit. A common complication occurs in the HVAC's compressor. There are several factors that could result in the compressor's unworkable status. Sometimes, the compressor may be unworkable because of an external interference. Sometimes, the problem is internal. Moreover, there are times when you have a poor HVAC compressor. Look for the different signs and symptoms of trouble and complication. If problems persist, a new HVAC compressor or system may be recommended.

Power Complications

  • A simple problem could be the power supply. If there is malicious wiring or breaks in the wiring, there may not be enough power transferring from the power source to the compressor. The faulty wiring can exist anywhere along the power cord, even into the compressor. The manufacturer recommends a certain voltage for the compressor. The power supply should stay within 10 percent of that recommended voltage level. Also, as another power complication, the compressor's low-voltage transformer could be defective. The low voltage produced by the transformer is used to close the contactor, which is part of the compressor's power supply system. If it is not closed, or the contactor's contacts are not pulled in, there will not be ample power transference to the compressor.

Discouraged "Open" Status

  • In some cases, the problem stems back to the contactor's open position. Sometimes, the compressor's thermostat will give a false reading. It will read that the compressor needs to cool, but it is because the contactor is still open. Though it is reading excessive heat, there is not ample power supply to the compressor.

    Also, there is the internal protector. This thermal switch protects the motor windings from excessive heating by opening ventilation. Check the motor windings with an ohmmeter. Before the motor windings can be checked, drain all refrigerant, remove all wires and turn off the power. Allow time for the compressor to cool.


  • The most common compressor problem is electrical overcharge. An electrical overcharge can come from dirty coils or a slow fan. This will result in low suction, and low suction may give a technician false premise to give additional charge to the unit. Most overcharging is done while trying to raise the compressor's suction pressure. Also, the run capacitor, which helps improve the energy usage of the motor, can affect the compressor's output. If the run capacitor fails, the motor will draw 10 percent more energy than it should, resulting in overheating. Should the run capacitor fail, it will look distorted and will need to be replaced.

Compressor Start-Up

  • There are cases when the start gear is faulty. It gives the compressor an extra boost of energy at start-up for its motor windings. Like the run capacitor, if the start gear fails, it will look distorted and will need to be replaced. Also, there is the refrigerant. The refrigerant carries oil to the compressor's motor. If there is a lack of refrigerant, the compressor could stick or cease to operate, especially if it has been running an extended amount of time with low refrigerant. It is similar to a vehicle's engine locking up or stalling from low oil amounts.


  • Photo Credit Pompe à chaleur image by mattmatt73 from electricity image by Mat Hayward from Tubes image by Thomas E. Schneider from
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