What Is Car AC Compressor : Types, Working, Symptoms & Replacement Cost

car ac compressor

The AC compressor is an important part of the air conditioning system of vehicles because it compresses the refrigerant for the operation of the air conditioning system. Typically, a bad AC compressor can exhibit several symptoms.

In this article, we will learn in detail about AC compressors in cars. Like, what is a car AC compressor, and how does it work? What are the symptoms of a bad AC compressor, and how much does a replacement cost?

What Is A Car AC Compressor

The AC compressor is a power component of the air conditioning system that compresses and liquefies the refrigerant gas before sending it to the condenser. It acts as a pump and plays an important role in the circulation of refrigerant and the production of cool air inside the vehicle cabin.

The AC compressor in vehicles is rotated by the power of the engine, which compresses the refrigerant with high pressure and temperature, and the compressed gas is then sent to the condenser, where the refrigerant cools and turns into a liquid state.

The refrigerant then returns to the evaporator, expands through the expansion valve, and absorbs heat from the surrounding air, thereby cooling the evaporator. As long as the blower is kept on, this process continues continuously, providing a continuous flow of cool air into the car interior.

Symptoms of Bad Car AC Compressor

Common symptoms of a bad car AC compressor are insufficient cooling, grinding or squealing noises, increased engine load, cooling stops, compressor overheating, clutch not engaging, or compressor leakage.

Let us know these symptoms one by one in detail, so that you can identify the bad AC compressor.

1. Sudden Stop Cooling


Often, the symptom of AC compressor failure in cars or other vehicles is a sudden lack of cooling while the AC is running and the AC blower starts blowing hot air.

Suddenly, the temperature starts rising in the cabin of the vehicle. The reason for the sudden stop of cooling is the failure of the AC compressor. Due to which the functioning of the air conditioning system of the vehicle is completely disrupted. However, the sudden stop of cooling can also be due to malfunctions in other parts of the air conditioner system. like a sudden fuse blowing in an AC compressor or damage to wiring, etc.

2. Refrigerant Leaking

Refrigerant fluid flows through the vehicle’s air conditioning system. Which is compressed through an AC compressor. But due to a bad gasket or seal on the AC compressor, refrigerant starts leaking. This leak can be mild or severe, depending on the type of compressor.

If the AC compressor’s gasket or seal is excessively leaky, refrigerant can leak out more rapidly, causing the air conditioning system to shut down completely. Refrigerant leakage can also be a symptom of a bad AC compressor. Be sure to check the AC compressor if refrigerant is leaking.

3. High Back Pressure

If you are filling refrigerant in the air conditioning system of your car or vehicle. You will then see back pressure in the pressure gauge of the AC compressor as the compressor spins.

The back pressure in the low pressure line of a properly functioning AC compressor should generally be between 30 and 40 PSI. But if the AC compressor is bad, then the low pressure line will show back pressure above 40 PSI. And it can display back pressure from 60 to 80 PSI.

4. Unusual Noise

Sometimes an unusual sound starts coming as soon as the AC of the car is turned on. This kind of unusual noise can also be a main symptom of a bad AC compressor. This type of unusual noise as soon as the car’s AC is started can have many different causes, including a bad compressor. Unusual noises in a bad car’s AC compressor may be due to bad bearings or worn pistons.

5. AC Compressor Clutch Not Engaging

A car’s AC compressor has a pulley, which rotates freely through a continuous serpentine belt as the engine starts. But as soon as the air conditioner system starts, the clutch magnet attached to the pulley of the AC compressor gets stuck to the pulley rotating through the coil, due to which the AC compressor starts working and provides cooling to the air conditioner system.

But many times, even after switching on the AC, the compressor does not stick to the clutch pulley and does not rotate, due to which the AC compressor does not start. So a compressor clutch that remains stable even when the AC is on

6. Worn or Broken Serpentine Belt


As you may know, the AC compressor in cars or other vehicles is rotated by the power of the engine through a serpentine belt. But sometimes the car’s AC compressor gets completely jammed due to a broken bearing on the compressor or a broken piston inside.

Due to which the serpentine belt breaks due to excessive friction. This can also be a symptom of a bad AC compressor. However, the serpentine belt can also break due to a broken or jammed water pump, alternator, power steering pump, or adjuster bearing.

Causes Of A Failure Car AC Compressor

There can be many different reasons for a car AC compressor going bad. Which can be like this.

1. Damage Wiring or Blown Fuse


To start the car’s AC compressor, a clutch is engaged with a pulley that rotates continuously. This clutch engages the pulley that rotates when the air conditioner system is turned on and it sticks to the clutch pulley with the help of a magnet coil. When we turn on the AC button, the power supply comes from the magnet coil.

And due to the magnet force, the clutch sticks to the compressor’s pulley. Due to which the AC compressor works. But sometimes the car’s AC compressor wiring gets damaged or a fuse blows. Due to this, the AC compressor does not turn on even when the AC button is turned off. Bad wiring or a blown fuse is the main reason for a bad car AC compressor.

2. Burnt AC Clutch Magnet Coil

brunt ac clutch coil

In a car’s AC compressor, a magnet coil is used to make connections with the clutch and pulley. But sometimes the magnet coil gets burnt due to overheat. Due to which the AC compressor does not turn on even after pressing the AC buttons.

3. Low Refrigerant Charge

Refrigerant low charge can also be the reason for AC compressors not working in cars or other vehicles. Because of this, the compressor is not able to pressurize the refrigerant completely.

4. Over Filled Refrigerant

Sometimes the refrigerant in the car’s AC system is overfilled. Due to which the AC compressor becomes unable to compress the refrigerant. Due to which the piston of the compressor gets stuck due to high pressure and the AC compressor gets jammed.

5. Damage Bearings & Pistons Plate inside

All types of AC compressors in cars have bearings. These bearings make the rotational motion smooth and friction-free. But sometimes the AC compressor gets stuck due to a breakdown of the bearing. This situation can also occur due to a broken piston inside the compressor. This can be a serious problem. Because if this happens, your serpentine belt will break.

Types of Car AC Compressor

  • Rotary AC Compressors
  • Variable Displacement AC Compressors
  • Scroll AC Compressors

How Does A Car AC Compressor Work

In an AC compressor, there are a number of small pistons that are rotated by engine power along a shaft in the compressor cylinder, and these pistons have spring-mounted blade plates to control pressure and vacuum.

This plate has two-faced, spring-like blades. When the refrigerant is compressed, these blades seal the area inside the cylinder, and as pressure builds on the other side of the cylinder, the spring opens, causing the compressed refrigerant from one side to flow out the other side.

The functions of a car’s AC compressor are composed of two sections. There is a high-pressure area and a low-pressure area. A suction cycle in a car’s AC compressor draws refrigerant from the air conditioning system and compresses it.

Upon compression, this refrigerant is sent to the AC condenser. The condenser converts hot gas from the air conditioning system into cold gas, and when cooled, the refrigerant is forced to flow through the expansion valve to the cooling coil.

Due to this, the evaporator absorbs heat from the surrounding air, and the blower fan passes the air through the middle of the evaporator, where the cold air reaches the cabin of the vehicle.

Car AC Compressor Replacement Cost

On average, a new AC compressor replacement cost can range from $900 to $1500. A car AC compressor can cost $500 to $800, and mechanic labor costs can range from $400 to $700.

The replacement cost of an AC compressor in cars varies depending on the vehicle model, the mechanic’s labor cost, and the location. Because an independent mechanic can be cheaper than a certified garage mechanic.


Q.  How To Tell If Car AC Compressor Is Bad?

You can detect a bad car ac compressor by its symptoms. Symptoms of a bad car ac compressor can be as follows.

  • Hot air blowing through the vents even when the air conditioner is on.
  • Unusual noise coming from a compressor.
  • Refrigerant leakage.
  • AC compressor clutch not engaging.
  • Smell of burnt wires due to overheating from the compressor.
  • Smoke coming out of the compressor when the AC is on.
  • Serpentine belt breakage due to jammed AC compressor.

Q. Can you drive with a bad ac compressor?

No, the vehicle should not be driven with a bad car AC compressor. Because this can cause your vehicle’s entire air conditioning system to fail. And if there is a bad AC compressor that jams while burning, Then, with certainty, the serpentine belt of your vehicle will break. Due to which other functions of your vehicle can also be stopped completely. And the engine may also overheat.

Q. How long do car ac compressors last?

The lifespan of this car’s AC compressor usually depends on your care and the quality of the compressor. If you service your vehicle’s air conditioning system from time to time, Then the AC compressor in your car can run easily for 6 to 10 years.

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