Troubleshooting AC Compressor: How to Find the Most Common Issues

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Last updated: 
August 17, 2017

These troubleshooting AC compressor tips will assist you in determining if the compressor is the problem.

If so, let's see together what the specific issue might be.

troubleshooting ac compressor

Why You Might Need AC Compressor Troubleshooting Tips

If your central air conditioner isn’t working at all or is not adequately cooling your home, it is easy to suspect the compressor because it is the heart of central air conditioning. An AC compressor circulates refrigerant. This is the substance that captures heat inside your home and dumps it outside to cool indoor air.

However, compressors are often blamed when issues like these are causing the problem:

  • The circuit is off: Check the circuit in the electrical box and the one mounted on a wall near the condensing unit. A circuit that continues to trip indicates a wire or compressor problem.
  • Furnace/air handler filter: A heavily clogged filter can prevent the airflow enough for adequate cooling.
  • Iced up indoor coil: If the indoor coil is dirty, it will eventually stop the transfer of heat and cause the unit to freeze up. Turn off the AC, and run the system in fan-only mode until the ice melts. Clean the coil, and restart the system.
  • Condenser fan: With the power on, set the thermostat to AC with a set point below the home’s indoor temperature. Check to see if the condenser fan at the top of the condensing unit starts. A condenser fan motor that is locked up will prevent the compressor from starting.

Tools to Keep in Mind

The main tool used to check AC condenser components is an electric multimeter. Troubleshooting AC compressor wiring requires one. If you have a multimeter and know how to use it, locate the C, R and S terminals. Check for continuity between C & R, C & S and R & S. Resistance should be less than 30ohms.

While checking continuity, look for obvious signs of loose, broken, chewed or burned wiring. If there’s continuity and no obvious wiring issues, then troubleshooting AC compressor issues is the next step.

Troubleshooting AC Compressor Problems in 5 Steps

Here are common AC compressor problems and what causes them.

1. Check Fuses and Wiring

Symptom: The AC turns on and off frequently.

Solution: Known as hard starting and short cycling, this problem prohibits adequate cooling and will quickly ruin the compressor. Internal fuses and faulty wiring are the most common causes of hard starting. If you’ve ruled out those causes, adding a hard-start capacitator that gives the compressor additional torque to get started might work. These devices are helpful when an aging capacitor needs a boost. Moreover, installing one 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: The most common cause of this issues is a failed start capacitor. Replacing it is one of the simpler AC compressor repair issues. If replacing the capacitator doesn’t help, the compressor motor is probably wearing out. If the problem is that a fuse or circuit is being tripped, then repair is possible. Also, if not protected by fuse or circuit, the compressor will soon burn out or lock up. Then, the compressor or entire condensing unit will need replacing.

3. Check Refrigerant Level

Symptom: The unit isn’t cooling sufficiently.

Solution: If you’ve already checked the filter and evaporator coil, then the system might not have sufficient refrigerant charge. A leak is the most common cause of this issue. Troubleshooting AC compressor leaks is difficult without training and the right equipment. Repairing and recharging the system requires a refrigerant handling license.

4. Check Pressure Levels

Symptom: Inadequate cooling and/or short cycles because pressurization is too high or low.

Solution: Excessive suction pressure and low discharge pressure prevent proper circulation of refrigerant. So, it can’t remove enough heat to keep up with cooling demand. The pressure levels must be checked, and pressure switches or valves will likely require 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 making cold air, a broken valve in the compressor is a likely cause. It can’t be diagnosed, but is usually determined to be the issue when everything else is ruled out.

Caution Notes

Working on equipment powered by electricity includes the risk of shock causing injury or death. Turn off the circuit when inspecting your condensing unit and compressor for loose, burned or chewed wiring or if you choose to attempt a DIY repair. When working on powered equipment, always use insulated tools to prevent shock.

You won’t be able to buy refrigerant. As we eluded to, EPA regulations (40 CFR Part 82, Subpart F) under Section 608 of the Clean Air Act require that:

Technicians who maintain, service, repair, or dispose of equipment that could release ozone depleting refrigerants into the atmosphere must be certified.

It is illegal to sell refrigerant to anyone who does not have a certificate.

Replacing the Compressor vs. the Entire Unit

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

An HVAC representative can estimate the cost of the repair and the cost to replace the condensing unit. We hope this assists you in finding a quick fix or deciding to call an HVAC technician for repair estimates. Troubleshooting AC compressor problems is complicated. So, perhaps your friends and followers would benefit if you share this information with them.

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