How to Identify and Replace a Bad AC Compressor

In this article, you will know about the importance of the air conditioning (AC) system in a car, how AC compressors work, and reasons they may stop working. At the end of the article, you can follow the step-by-step guidelines to repair and replace AC compressors.

Why Are Air Conditioning System Important?

  • Air conditioning systems have become one of the most integral systems in a car. Air conditioners help to maintain the temperature and conditions inside the car. They make your trip comfortable and pleasant.
  • Air conditioning is not one of the most important systems in your car. A broken air conditioner might not bring your car to a halt. In fact,our car can run for many miles without air conditioning compressors. But have you ever seen a car without air conditioning system? 
  • An AC compressor is the main component in the air conditioning system. You can hear of AC compressor problems in the most luxurious and prestigious cars. The AC compressor is one of the most stressed components in any car. Some problems with an AC compressor might seem small and manageable, but they might end up as a very expensive issue over a long period of time.

Simple And Complete Operation Of The Air Conditioning System

Not only does an air conditioner cool the air, but it also reduces the moisture or humidity present in the air. Now, let us take a closer look at the specific parts of air conditioning system and their function.

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    Refrigerant – The fluid that passes through the entire system. The refrigerant evaporates at low temperature and condenses back at high pressure. The most common refrigerant used is R-134A.
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    Compressor – The compressor is the main component in the air conditioning system. It is connected to the crankshaft by a belt mechanism and powered. In hybrid vehicles, they are powered by electricity. The compressor pumps the refrigerant to the condenser.
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    Condenser – The condenser is used to convert high-pressure vapor into liquid. It is mounted at the front end of the car near the radiator. This helps to remove heat from the condenser that is created during liquidation process.
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    Receiver Dryer – The receiver dryer removes the moisture content present in liquid refrigerant. This is vital as moisture content may cause blockages or mechanical damage in the system.
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    Evaporator – The evaporator changes refrigerant to a vapor state and absorbs heat. The evaporator is located near the car’s dashboard. The cooled air from the evaporator is circulated in the car.
Automobile air conditioner servicing

Read this article for a more in-depth understanding and operation of the air conditioning system in your car.

This video shows the important parts and operation of the air conditioning system in an easy to understand animated version.

How to Identify Common Causes for AC Compressor Failure

AC compressor failure may cause the air conditioning system in your vehicle to stop working altogether. Before getting our hands on the compressor, you will want to identify the source of the problem. The failure of the AC compressor might be classified as two types as: external failure or internal failure.

  • External failure
  • Internal failure

Internal-And-External Failure

External Failure

 External failure is a better scenario in the AC compressor repair. The malfunction of the exterior components in the compressor leads to external failure. AC compressor failure may be due to any of the following reasons:

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    Loss of Power – The compressor is powered from the crankshaft of the engine. The clutch used to engage the compressor and crankshaft might be misaligned. Clutch misalignment causes no power transmission to the compressor. In electrical and hybrid vehicles, the compressors are electric powered, so the electric power supply lines must be checked.
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    Low Refrigerant Level – a small amount of the refrigerant circulating in the pump can be lost due to a leak, evaporation, or other reasons. The loss of refrigerant may lead to improper cooling by the air conditioning system.
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    Control System Failure – The air conditioning system is controlled by the electrical switches and a control system. The control system or switch failure will lead to a loss of signal to the compressor. The compressor will not turn on when the AC switch is engaged.

Internal Failure

Internal failure is one of the worst scenarios in the AC compressor failure. Internal failure of the compressor damages the internal parts and might lead to complete failure of the AC compressor. In some cases, the entire compressor system must be replaced as repair is impossible. Internal failure is caused mainly due to oil starvation and contamination.

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    Oil Starvation - The loss of oil lubricants will lead to heat build-up and wear in the internal parts of the compressor. This might end up in complete failure of the compressor system. The oil levels must be maintained for proper operation of the compressor.
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    Contamination – Debris or solid wastes might enter the compressor through the blower. The debris may disturb the operation of the compressor and lead to wear-and-tear of the internal compressor parts. Contamination may lead to the replacement of the entire compressor assembly.

How to Replace an AC Compressor.

After understanding about the AC compressor system working and different problems that cause the failure of the AC compressor system, we can move to the repair or replacement of the AC compressor. Never attempt to repair the AC compressor system unless you have proper knowledge and guidance combined with safety equipment and machine tools.

  • Step 1: Park your car in a safe place in such a way. Wear eye goggles and safety gloves for your protection. Always turn off the compressor and car system before beginning any repairs on your vehicle.
  • Step 2: Next, we must identify the reason for the malfunction. epending upon the problem, we should decide whether to replace or repair the compressor. Turn on the compressor and check whether your compressor is not operating or just not providing cool air to the car cabin.
  • Step 3: If your compressor is not turning on, it may be due to loss of power supply or failure in the control system.Check the belt drive from the crank assembly for proper clutch engagement. If all seems normal, check the electrical control system to provide proper signals to the compressor. Go through your car’s operation manual before repairing or working on the control system.
  • Step 4: Now my compressor is running and cooled air is not produced at the car. Then check the blower fan for proper operation. The blowers might not supply the cold air output to the car cabin.
  • Step 5: The loss of refrigerant in the compressor system may cause improper cooling, so you must check the compressor for proper refrigerant level. If the refrigerant level is low, charge the refrigerant in the compressor. To do this, vacuum down the refrigeration system and add the refrigerant in the supply line. Click here to find the step by step procedure to vacuum down and add the refrigerant in the compressor system.
  • A good vacuum pump and pressure gauge is required to charge the refrigerant. Click on the below links to find available refrigeration kits.
XtremepowerUS 3CFM or 4CFM Air Vacuum Pump HVAC A/C Refrigeration Kit AC Manifold Gauge Set ( 3CFM 1/4HP Air Vacuum Pump)
  • Step 6: Remove the compressor by removing all the bolts and nuts attached to them. Now check if your compressor is not working due to internal failure. Check the extent of the damage caused to the compressor. Disconnect the battery lines to avoid electrical shock.Seal the refrigerant lines to avoid leakage of refrigerants while removing.
  • Step 7: In the case of debris and solid waste accumulation, try flushing your compressor. The compressor must be flushed multiple times to properly clean the compressor system.
  • Step 8: Check the old compressor for failure and determine if the compressor can be repaired. 
  • Step 9: A new compressor must be added with suitable lubricant oil for smooth and effective operation. Click this link to find the reccomended oil amounts and levels.
  • Step 10: Match the O-rings in the compressor to provide proper seal in the compressor system. Always use new O-rings whenever you dismantle your compressor. The older O-rings may be flattened due to pressure.
  • Step 11: Next, gently move the new compressor into the engine bay. Clear all the hoses and lines carefully. Thread all the mounting bolts and nuts to hold the compressor in line. Then connect the refrigeration lines in the compressors and belt drive mechanism to the crankshaft.
  • You can follow this handy guide and follow the step-by-step guidelines to dismantle and replace an AC compressor. You can also follow the guidelines shown in this video to replace and repair an AC compressor.


Your new AC compressor should be running well now. AC compressor replacement might cost you a lot of money at a service center. You can save that money by following the AC compressor replacement steps mentioned in this article.

AC compressor failure might now stop your car completely, but they may spoil the travel experience of you and your passengers. AC compressors are necessary to experience a comfortable and enjoyable travelling experience.


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Hi there! I’m Jordan, chief editor of Crush the Road and I’m a self-confessed automative fanatic. Cars or vehicles has always been a passion of mine and will always be my favorite pastime. Now that I am married and has one adorable son, I have the time to write and share my personal experiences with other automative enthusiasts like me. Welcome to my fantastic blog!

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