How to Diagnose & Repair An Old AC Compressor


The air conditioner’s compressor is the heart of the system and plays a crucial role in the cooling process. A properly functioning compressor means a properly functioning AC unit.

However, sometimes, due to continued usage, age, and other numerous factors, the compressor might stop functioning, thereby causing the entire AC system to malfunction. It is thus critical that you diagnose and repair the AC compressor for a flawless HVAC system.

Diagnosing and repairing an AC compressor can be quite a complex process that requires specialized knowledge and expertise. Thus, the best way forward is to seek professional help. HVAC technicians can easily diagnose the issue and carry out the necessary repairs safely and efficiently.

For anyone looking to take on AC Repair in Fort Mohave, AZ, note that it can be a safe and easy process if you know what to look for. Keep reading as we explore the different steps involved in diagnosing and repairing an AC compressor which will help you understand the process and the importance of regular maintenance.

How to know you have a bad AC compressor?

An AC compressor that develops problems will generally give some signs. It is important to look for these signs to understand whether your AC compressor is working properly. Some of the most common symptoms are as under.

  • Unusual loud noises like grinding, hissing, or squealing coming from the AC unit compressor are indicative of a compressor that has developed problems with its bearings or other mechanical components.
  • Warm air coming from the AC system instead of cool air might mean that your AC compressor has developed serious problems. The primary function of the compressor is to blow cool air, and anything otherwise means it’s not working properly.
  • If you notice that the airflow from the AC system is weak or reduced, this might mean that the compressor is facing an issue. The compressor helps circulate the refrigerant, which cools the air, so the airflow will be affected if it goes bad.
  • Higher than usual energy might be indicative of a malfunctioning compressor. It can cause the AC system to work harder, which would mean much higher energy consumption and relatively high energy bills.
  • If the AC system faces an issue switching on, chances are that the compressor is not working. Electrical issues with the compressor or other components can sometimes prevent the system from switching on.

How to diagnose an old AC compressor physically?

Diagnosing an old AC compressor can be a challenging task. This is because the AC system is quite complex and requires specialized technical expertise. An HVAC technician cut out for the job thoroughly understands electrical wiring, refrigerant properties, and mechanical components.

Also, working with an AC compressor involves handling high-voltage electricity and refrigerants, which can be extremely dangerous. There are high chances of injury or property damage without proper training and equipment. However, there are certain methods to diagnose a faulty old compressor, provided you are up for it.

Inspecting the compressor

First, you need to inspect the compressor for any visible damage or wear and tear. It is important to look for signs of rust, leaks, or cracks on the compressor.

Check the electrical connections

Inspecting the electrical connections comes next to ensure they are tight and not corroded. Also, make sure to check the fuses and circuit breakers. This will give you an idea of whether they are blown or tripped.

Measure the voltage

Measure the voltage across the compressor terminals using a multimeter in order to determine if the compressor is receiving the correct amount of power which is crucial for a functioning Ac compressor.

Test the capacitor

The capacitor’s job is to start the compressor. If it is broken or not working, the compressor may not start. Testing the capacitor using a capacitance meter is thus essential. You can also visually inspect it for signs of bulging or leakage.

Check the refrigerant levels

Low refrigerant levels can be one of the major causes of a malfunctioning compressor. In that case, you can use a refrigerant gauge to measure the refrigerant levels in the system.

Check the oil levels

There must be adequate oil in the compressor. If the oil levels are low, the compressor may not work properly.

How to repair the faulty compressor?

Once you have identified the problem, you can determine the right course of action for repairs. In many cases, a faulty compressor is the result of a minor issue like a low refrigerant level. Sometimes, the issue can be more serious, like faulty electrical components or a damaged compressor motor.

Provided below is a stepwise guide on repairing the AC compressor. The best process, however, is consulting an HVAC technician.

Disassemble the compressor

You must first disassemble the AC system to access and repair the compressor. This involves disconnecting the electrical connections, removing the refrigerant, and disassembling the compressor unit. Then, you can start working on the individual components of the compressor.

Replace faulty components

Identification of faulty component(s) must be followed by replacing that component. This component can be electrical, like capacitors or relays, or mechanical, like bearings or pistons.

Reassemble the compressor

After replacing the faulty components, reassemble the compressor unit. Ensure all the electrical connections are secure and the refrigerant lines are properly connected.

Test the system

Once the compressor is reassembled, it is important to test the AC system to ensure it works correctly. You need to check the refrigerant levels and ensure the compressor is running smoothly.


It’s essential to note that repairing an AC compressor can be dangerous and must always be done by skilled and trained HVAC technicians who can maintain proper safety protocols. Also, it requires special tools and physical fitness as the compressor might not be located at the easiest of locations.

Thus, if you’re unfamiliar with HVAC systems or do not own the necessary tools, it’s best to contact a professional technician to diagnose and repair the compressor.

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