Troubleshooting AC Compressor: How to Find the Most Common Issues

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Last updated: 
April 16, 2024

Troubleshooting AC Compressor Tips

If your central air conditioner isn't working properly or not cooling your home adequately, it's easy to suspect the compressor, as it is the heart of the system. The AC compressor circulates refrigerant, which captures heat inside your home and releases it outside to cool the indoor air. However, before assuming the compressor is the issue, there are several other factors to consider, according to our research.

Potential Causes of AC Issues

Before troubleshooting the AC compressor, check for these common issues that can affect your system's performance:

  • Tripped circuit: Check the circuits in the electrical box and the one mounted near the condensing unit. A repeatedly tripping circuit may indicate a wiring or compressor problem.
  • Clogged furnace/air handler filter: A heavily clogged filter can restrict airflow, preventing adequate cooling.
  • Frozen indoor coil: A dirty indoor coil can hinder heat transfer and cause the unit to freeze. Turn off the AC, run the system in fan-only mode until the ice melts, clean the coil, and restart the system.
  • Faulty condenser fan: With the power on and the thermostat set to AC with a temperature below the home's indoor temperature, check if the condenser fan at the top of the condensing unit starts. A locked-up condenser fan motor will prevent the compressor from starting.

Tools for Troubleshooting

An electric multimeter is the primary tool used to check AC condenser components and wiring. If you have a multimeter and know how to use it, locate the C, R, and S terminals, and check for continuity between C & R, C & S, and R & S. The resistance should be less than 30 ohms. While checking continuity, look for signs of loose, broken, chewed, or burned wiring.

5 Steps to Troubleshoot AC Compressor Problems

1. Check Fuses and Wiring

Symptom: The AC turns on and off frequently (hard starting and short cycling).
Solution: This issue prevents adequate cooling and can quickly ruin the compressor. Internal fuses and faulty wiring are the most common causes. If these are not the problem, adding a hard-start capacitor to provide additional torque may help, especially if an aging capacitor needs a boost. This can delay the need to replace the unit for several years.

2. Check the Start Capacitor

Symptom: The compressor won't start or stops shortly after starting.
Solution: A failed start capacitor is the most common cause. Replacing it is one of the simpler AC compressor repairs. If replacing the capacitor doesn't help, the compressor motor may be wearing out. If a fuse or circuit is being tripped, repair is possible. However, if not protected by a fuse or circuit, the compressor will soon burn out or lock up, requiring replacement of the compressor or entire condensing unit.

3. Check Refrigerant Level

Symptom: The unit isn't cooling sufficiently.
Solution: If the filter and evaporator coil have been checked, the system may have insufficient refrigerant charge. A leak is the most common cause, but troubleshooting AC compressor leaks is difficult without training and proper equipment. Repairing and recharging the system requires a refrigerant handling license.

4. Check Pressure Levels

Symptom: Inadequate cooling and/or short cycles due to high or low pressurization.
Solution: Excessive suction pressure and low discharge pressure prevent proper refrigerant circulation, hindering heat removal and cooling. Pressure levels must be checked, and pressure switches or valves may need replacing.

5. Replace the Compressor

Symptom: The compressor runs but doesn't cool.
Solution: If everything seems to be working normally, but the AC isn't producing cold air, a broken valve in the compressor is a likely cause. This can't be diagnosed directly but is usually determined when all other issues have been ruled out.

Caution and Considerations

Working on electrical equipment carries the risk of shock, which can cause injury or death. Always turn off the circuit when inspecting your condensing unit and compressor for loose, burned, or chewed wiring, or if attempting a DIY repair. Use insulated tools to prevent shock when working on powered equipment.

It's important to note that, according to EPA regulations (40 CFR Part 82, Subpart F) under Section 608 of the Clean Air Act, technicians who maintain, service, repair, or dispose of equipment that could release ozone-depleting refrigerants into the atmosphere must be certified, and it is illegal to sell refrigerant to anyone without a certificate.

Replacing the Compressor vs. the Entire Unit

Some manufacturers, like Goodman and Amana, offer warranties that provide replacement of the entire condensing unit if the compressor fails. However, most do not, and even if the compressor is under warranty, labor costs are usually not covered. If your compressor has failed, replacing the entire central air conditioner might be a better option than repair. This allows you to select a unit with higher efficiency and superior indoor climate control.

An HVAC representative can provide estimates for both repair and replacement of the condensing unit. We hope this information assists you in finding a quick fix or deciding to call an HVAC technician for repair estimates. Troubleshooting AC compressor problems can be complicated, so sharing this information with friends and followers may benefit them as well.

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