3 Signs Your Car's AC Compressor is Failing

AC compressor replacement

When the temperature gets steamy outside, the air conditioning system keeps your car’s interior comfortable by circulating refrigerant throughout the AC system.

The AC compressor pressurises the system to push the refrigerant throughout. Through normal wear and tear, and possibly due to an unexpected defect, the AC compressor may stop functioning or seize.

In many situations, the AC compressor lasts the whole life of the vehicle without requiring replacement, although failure is more likely after 150,000km.

On average, you can expect AC compressor replacement to cost $800 to $1,200 or more, depending on the make and model you drive.

Because it’s a cornerstone component of your air conditioning, your AC won’t function if the compressor is broken.

What is an AC compressor?

At the basic level, an AC compressor is a mechanical pump. It pressurises and circulates the refrigerant in your car’s AC system.

In turn, the rest of your AC system enables that refrigerant to cool the air that enters your car, but it all starts with the compressor.

An electrically-activated clutch on the compressor engages when the system detects lowering pressure. Inside the AC compressor, two pistons attached to a wobble plate pump the low-pressure refrigerant entering the compressor into the high-pressure side.

This cycle continues as long as the AC system is activated or the defogger is turned on.

A small amount of oil is required to lubricate the moving components.

The clutch mechanism utilises a bearing that can fail as well.

And if one of the seals or internal parts in the AC compressor develops a flaw, the compressor won’t function as it should or not at all, and will need to be replaced.

Symptoms that your AC compressor requires replacement

  • Clunking noise when clutch engages instead of light click
  • Warm air blowing through dash vents with AC system turned on
  • Broken serpentine belt from seized AC compressor clutch
  • External leak detected by technician’s diagnosis
  • Windows fog up in humid weather
                  How is AC compressor replacement

How is AC compressor replacement performed?

  • The technician recovers the refrigerant in the whole AC system, discharging any pressure
  • The serpentine belt is removed from the AC compressor clutch pulley and the clutch is unplugged
  • The low-side and high-side refrigerant lines are disconnected from the compressor body
  • The failed compressor is unbolted and removed, and a new AC compressor fitted
  • The lines are refitted and the belt and wiring put back in place
  • The AC system is recharged with refrigerant according to manufacturer’s specifications
  • The technician confirms the AC system’s operation

Tips to remember

  • Refrigerant should always be recovered safely by a certified technician as releasing it into the environment is known to be harmful
  • A leak elsewhere in the AC system can seem like a failed compressor. Proper diagnosis by approved technicians can eliminate needless repairs

How important is replacing your AC compressor?

You may think it’s designed only to keep you cool. While it does so, the AC compressor also draws moisture out on the defog settings, maintaining clear windows so you can see.

Typically, a failed AC compressor won’t cause safety-related concerns but instead an annoyance for the driver and discomfort for all occupants.

If you’ve read this far, you obviously care about your car. A lot. So next time you need a service, repair or inspection, visit AutoGuru.com.au.

We let you search and book from over 1600 qualified mechanics, who eat car troubles for breakfast.


Next Step

Schedule Car AC Compressor Replacement

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  • Delphi Technologies covers more than 3,400 applications.
  • Supplies a/c compressors for 1989 to present applications.
  • Provides HVAC components to eight of the top 11 OEM global manufacturers.
  • The majority of Delphi Technologies compressors are made in North America.
  • No extra parts to purchase or stock. Sealing washers included with all compressors (when applicable).
  • Our compressors are leak tested to one pound of refrigerant in 40 years using sophisticated mass spectrometer leak test equipment.

AC Compressor Clutch Location

The AC compressor clutch is found in front of the

The AC compressor clutch is found in front of the compressor. When you turn the air conditioning on, the clutch engages and spins during normal operation. 

To find the AC compressor, look at the front of the engine where the other belt-driven accessories are found. 

Compressor Maintenance

Because it is a sealed system, the only maintenance that the typical AC compressor needs is regular use to keep lubricant dispersed throughout the system. When addressing air conditioning problems, refrigerant charge is important to consider, because excessive or insufficient pressure may disable the system. Drive belts need to be clean and tight for positive engagement. Finally, electrical checks confirm proper function of pressure sensors and switches; electromagnetic clutch fuse and relay; and the clutch coil.

Oil type and viscosity depend on the refrigerant and the compressor. For example, R-134a compressors are lubricated by polyalkylene glycol (PAG), which may not be compatible with proprietary R-1234yf compressor oils. Viscosity is also important, as lighter PAG 46 oils may not protect compressors requiring heavier PAG 100 or PAG 150 oils.

Maintaining Your A/C Compressor

Thankfully, maintenance of your A/C compressor is rather minimal and includes the following:

● Regularly use the compressor in order to keep all of the elements of the system properly lubricated. ● Charge your refrigerant to ensure the proper levels of pressure in the air conditioning system. ● Clean and tighten the drive belts as necessary. ● Perform electrical checks on the switches and sensors, as well as the EM clutch’s fuse, relay, and coil.

The most common reasons that an A/C compressor will fail are wear-and-tear due to age or neglect. If you experience a compressor failure, you will need to replace it. It is important to remember that if you use one that has been re-manufactured, you need a recovery machine in order to protect your atmosphere while extracting the refrigerant. Note that while you can replace certain EM clutches, there are some that are replaced only as an assembly, as with all motor-driven compressors.

Final word

If you notice the symptoms of a bad ac compressor, the next thing you want to do is carry out a car ac compressor diagnosis to be sure the AC compressor is the culprit. Replacing a vehicle ac compressor yourself can be an expensive, time-consuming fix. The ball is in your court to decide whether or not you want to replace the AC compressor yourself. The fact is, the summertime can get incredibly hot. Sweating and driving during a hot afternoon might not be something you want to experience.

Easy installation of an air conditioning compressor

When it comes to A/C servicing, first time fit and reliability are critical. Our compressors are designed with this in mind and come with an exterior shell casting that matches the OE part, together with all the required accessories for quick and easy installation.

What Can Stop The Clutch From Engaging?

These are some of the plausible reasons the compressor clutch isn’t engaging with the compressor:

  • Excess refrigerant
  • Insufficient oil in the compressor
  • Inadequate refrigerant

Default Lockout On The Clutch Sensor

Most modern-day vehicles feature AC compressor clutches that are switched on and off via the low pressure and high-pressure switches, as well as the level of compressor oil. These 3 aspects can disable the clutch and stop it from engaging if the sensor finds insufficient oil, inadequate, or too much refrigerant.

Burnt Fuse

Turn off the car engine and detach the fuse from the system to know if the fuse is burnt. Use a multimeter to check the fuse. Alternatively, any instrument that can gauge the situation can help. If the fuse is fine, return it to its initial place.

Poor Air Conditioning Performance

Perhaps the most obvious sign of a compressor issue is poor air conditioning performance. If you notice your cabin feeling warmer than usual or your air conditioner is blowing warm air, you know that your system is experiencing some troubles. 

Vehicle AC Compressor Problems vs. Low AC Refrigerant 

Poor AC performance can often be traced back to either compressor failure or low AC refrigerant. Unfortunately, these vehicle components work hand-in-hand, making it hard to distinguish which is causing your AC troubles. So how can you tell if it is a compressor problem? There are a few subtle symptoms to look out for:

  • Freon Levels: If your AC system has optimal freon (refrigerant) levels (not too much or too little), but your air conditioner still does not work properly, this is often the sign of AC compressor failure.
  • Inconsistent AC Performance: Refrigerant leaks will only continue to get worse as the problem continues. On the other hand, a failing AC compressor might work well one day and poorly the next. While it is not applicable for all AC troubles, this symptom is an easy way to distinguish between low refrigerant and compressor problems. 
  • Sudden AC Performance Drops: Refrigerant tends to leak gradually over time, while AC compressors can stop working on a dime. While even small refrigerant leaks can cause large AC problems, sudden drops tend to indicate compressor failure.

If you are still unsure of the source of your AC problems, it might be time to bring your vehicle to a mechanic for professional insight. 

Prevent a Dead AC Compressor in the Future

As you can see, there’s a lot of troubleshooting that goes into fixing an AC compressor that won’t turn on. If you want to skip this laborious troubleshooting, you should know how to prevent this problem.

The biggest means of prevention is maintenance. You might want to get an AC tune-up from a car shop every spring so you can get ahead of the problem.

Mechanic inspecting the vehicle’s air-condit
Mechanic inspecting the vehicle’s air-conditioning compressor with a manometer.

Besides that, it’s a good idea to run the AC for 10-15 minutes once a month, regardless of how cold it is outside.

If you spend a little time and money today on maintenance, you can save a lot of money tomorrow. This is one of many ways to ensure your car lasts forever.

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Bottom Line

By now, you should be clear on how to test a car AC compressor using a multimeter. Typically, this is the one essential tool you cannot do without. After performing the test, you will be able to determine whether the AC compressor needs to be repaired or replaced.

AC Compressor Clutch Replacement Cost

The average AC compressor clutch replacement cost is between $700 and $1000. Labor costs tend to be about $150 to $250, with the new compressor costing $450 to $850. It’s not normally recommended to replace the compressor clutch, but rather, install a whole new compressor. 

Because the compressor is one of the main parts of the air conditioning system, it is an expensive part, probably the most costly of the entire system. However, it isn’t difficult to replace. 

If you plan to continue driving your vehicle, replacing the AC compressor is a no-brainer decision. However, you don’t want to take shortcuts and replace just the clutch, just to find out down the road that another part is bad and you need a new compressor anyway.


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