How To Diagnose And Fix AC Compressor In Your Car

1 Diagnosing AC Compressor Failure

During summer, a trip in the scorching heat can only be made less miserable with the use of air conditioning.However, a broken air conditioning system in your car can lead to an excruciating drive.  The AC compressor, which is at the core of the car’s AC system, plays a crucial role and if it fails, it can disrupt the entire functioning of your car’s AC system.  

The air compressor is responsible for compressing the freon or refrigerant, which then circulates throughout the system. If the compressor fails, the system no longer receives freon which stops the supply of cool air into the cabin. If you are experiencing air conditioning troubles then start by checking your air compressor and its related parts for any signs of failure. 

AC Compressor

AC Compressor Clutch

AC Condensor

AC Expension Valve

AC Lines

Serpentine Belt

Belt Tentioner

Comperrsor Clutch Bearing

AC Seal Repair Kits

AC Line Gaskets

Electronic Leak Detector

2 How To Diagnose AC Compressor Failure?

The air compressor is the central unit of the air conditioning system and ensuring its proper functioning is essential for its optimum performance. The vehicle’s AC compressor sustains immense pressure, heat, and constant wear and tear much like any other mechanical component in the vehicle, which can eventually lead to failure.

Check Cabin Air

The first sign of potential air compressor failure is hot air blowing from the AC vents. The freon is pressurized and pushed throughout the system with the help of the compressor and so if it fails, the AC system will not work properly. However, there are many other reasons for hot air coming from the AC vents like low refrigerant, excess oil, clogged condenser, defective thermal expansion valve, broken AC clutch, etc. Make sure to properly diagnose the air compressor before replacing it with a new one.

Check Compressor Drive Belt Condition

The drive belt commonly known as the serpentine belt is what drives the compressor using the engine’s power. This belt is connected to the crankshaft and spins on the compressor pulley. If the serpentine belt is worn or faulty then the compressor won’t get any power to run which means the AC in your cabin won’t function properly. Excess slack in the belt can cause slippage or can be too loose to even engage the pulley. Slack can be easily adjusted by tightening the bolt to the tensioner. But if the belt is worn, frayed, or in worse condition then replacing it is necessary. Also, if the belt tensioner is broken and cannot hold or apply steady pressure on the belt, then it may also need to be replaced.

Check Clutch Engagement

The next step is to check whether the compressor is being driven when the AC is switched on. The compressor is not in constant engagement with the engine, instead, it is operated when the compressor clutch is actuated that drives the compressor shaft. Most modern cars have an electromagnetic AC clutch which is part of the compressor pulley assembly. The clutch consists of a drive plate, pulley, bearing, and stationary coil. When 12v is applied to the coil, an emf is applied to the clutch drive plate which causes it to engage with the driven pulley. The clutch plate is directly splined or connected to the compressor shaft. So when the clutch is engaged with the driven pulley, the compressor shaft rotates and runs the compressor. 

The clutch and pulley assembly are often the components that cause the air conditioning system to fail, and therefore must be checked for proper functioning. To see if your clutch is engaging with the pulley you can open your hood and locate your air compressor. The front part of the pulley is the clutch drive plate. When the engine is running and the AC is switched off, you can see that this plate remains stationary but the pulley rotates with the belt. Now if you switch on the AC from the cabin, you should notice the plate starts moving with the pulley. Note that the compressor is directly controlled by the ECU which may intermittently stop and start the compressor based on its heat and the pressure in the system. So if you notice the clutch plate starts and stops after short spans, don’t be alarmed as it is simply the ECU maintaining optimal compressor performance. 

The clutch can go bad for various reasons like a bad relay, fuse, wiring issue, detective coil, or worn-out clutch friction surface. If the clutch does not engage then there can be an electrical issue that must be fixed. A simple way to check the electrical system is to apply 12v directly from the battery to the stationary coil or the clutch lead wire. Do this with the engine turned off. If the clutch does not move then the problem is most likely with the coil and if it does move, then the issue might be with the electrical system: fuse, relay, wiring, switch or control module.

Lastly, check the air gap between the clutch and the pulley. If there is too much clearance, the clutch can not engage at all or slip and run against the pulley causing excessive wear and heat leading to clutch plate failure. To check the gap, you can use a feeler gauge. Every compressor has different specs so you will have to refer to a service manual for the correct gap. Commonly the gap should be within 0.015 to 0.040-inch press fit clearance.

Check For Unusual Noises

If your clutch is successfully engaging and disengaging periodically, then you do not have clutch-related issues. With the engine and AC running at max, open the hood and listen for any unusual sounds like clunking, grinding, and squealing coming from the compressor and pulley assembly. A grinding noise could indicate the pulley or internal compressor bearing is faulty. A broken pulley bearing can be easily replaced but internal compressor bearings require a compressor replacement. A leaking bearing will also cause squealing noises to emanate from the compressor. A clunking noise indicates that the compressor has broken and the metallic debris in the compressor is slashing around causing an unsettling clunking noise. In this case, the only solution is to replace the compressor unit. The squealing noise can also be due to excessive belt tension. Try relieving the stress on the belt by loosening the tensioner assembly.

If you suspect that the pulley bearing is toast then you can verify that by checking for play in the pulley assembly. With the assembly attached to the compressor, try rocking the pulley back and forth, and If it wobbles or rocks then the problem lies in the pulley bearing. Replacing the pulley assembly is simple as they are sold separately from the compressor unit. It is also a good idea to swap out the clutch plate while you are at it to futureproof the compressor. 

Check For Leaks

The most obvious cause of compressor failure is leakage in the system or the compressor itself. A leakage causes the freon to deplete from the system. Since the compressor’s lubrication oil is part of the freon itself; low freon means low lubrication oil which causes the compressor to run dry, experience excessive heat, wear and tear and eventually seize or break. If your refrigerant level is too low then the AC in your car won’t work and the compressor will fail eventually which is why it is important to check, find and fix the leak in the AC system. 

There are various methods of detecting leaking freon such as using UV dyes and special UV flashlights for leak detection, ultrasonic sound detection or an electronic leak detector. The common leakage points or vulnerable areas where leaks are typically found are the AC line connection gaskets and seals, condenser, compressor connections or the compressor shaft seals, the condenser unit, etc. If you find a leak between connections then the issue may simply be a bad seal or O-ring in the AC system. A leak in the compressor can be a serious problem and will require a complete compressor rebuild or replacement. 

If your air compressor is not working because of any of the above given reasons then having it fixed is necessary to restore your vehicle’s air conditioning system. The air compressor is vital to the AC system functioning and maintains pressure and refrigerant circulation throughout the system and any irregularities in compressor functioning will directly affect the entire system. Most air compressors last for long if maintained properly with regular inspection and refrigerant and oil refills. Other components like the compressor clutch, pulley assembly, and drive belt need to be maintained and periodically checked for optimal performance. A bad clutch or pulley bearing will eventually do irreparable damage to the compressor and cause more expensive fixes. So make sure that the compressor and all its components are working efficiently for prolonged AC compressor life. 

3 FAQs

How to know if a compressor is bad?

If you’re experiencing issues with your air conditioner, it’s possible that the compressor is faulty. Here are some signs that could indicate a bad AC compressor:

1. Unusual noises: If you hear growling, screeching, or clattering noises coming from your AC unit, it could be a sign of electrical failures in the compressor.
2. Poor cooling: If your AC is not cooling properly, it could be due to a compressor problem. You can check if the compressor clutch is cycling on and off by cranking the AC to max.
3. Vibrations: If the condenser unit is vibrating, it could be a sign of a faulty compressor.
4. Hard time starting: If you’re having trouble getting your AC to start, it could be due to a tripped breaker or a blown fuse. Check the electrical service panel and the fuse box to rule out these possibilities.
5. Refrigerant leaks: If you see refrigerant leaks around the compressor, it could be a sign of a bad compressor.

How to check a compressor clutch?

To check if your AC compressor clutch is working properly, you can follow these steps:

1. Start the engine: Turn on the engine and let it warm up.
2. Locate the compressor: Stand in front of the AC compressor at the front of the engine.
3. Turn on the AC: Have an assistant turn on the AC controls to maximum.
4. Observe the clutch: Wait for the AC clutch in front of the compressor body to engage and spin. If it does not, shut the engine off and disconnect the negative battery cable with a socket.

How to remove excess freon from car ac?

To remove excess freon from your car’s AC, you can use an AC recovery machine to condense the freon to vapor and remove it from the AC system altogether. Here are the steps to follow:

1. Close the low-pressure service valve: Use a wrench to close the low-pressure service valve.
2. Attach the recovery machine: Attach the recovery machine to the low-pressure AC service port beneath your hood.
3. Remove the freon: Turn your vehicle on and run the AC. The recovery machine will condense the freon to vapor and remove it from the AC system. Wait for 5-10 minutes for the vacuum to finish. After it seems like the vacuuming is complete, wait another 20-30 minutes and turn the pump on again. This will help get any excess still left over from before.

How to fix a compressor in a car?

If you’re experiencing issues with your car’s air conditioner, it’s possible that the compressor is faulty. Here are some ways to fix a bad AC compressor:

1. Check the AC system pressure and the AC clutch engagement: Use a pressure gauge to check the AC system pressure and the AC clutch engagement. If the pressure is low or the clutch is not engaging, it could be due to a compressor problem.
2. Check the fuses, relays, and wiring for the AC clutch circuit: Check the fuses, relays, and wiring for the AC clutch circuit. If any of these components are faulty, it could cause the AC compressor to malfunction.
3. Test the resistance and power of the AC clutch coil and connector: Use a multimeter to test the resistance and power of the AC clutch coil and connector. If the resistance or power is not within the manufacturer’s specifications, it could be due to a faulty compressor.
4. Remove the refrigerant, the belt, and the compressor from the vehicle: If the compressor is faulty, remove the refrigerant, the belt, and the compressor from the vehicle.
5. Install the new compressor and the belt: Install the new compressor and the belt. Make sure to use the correct type of refrigerant and oil.
6. Vacuum and recharge the AC system with the correct amount of refrigerant: Vacuum and recharge the AC system with the correct amount of refrigerant. This will ensure that the AC system is working properly.

What does a bad ac compressor sound like in a car?

A bad AC compressor in a car can produce a variety of sounds, including:

• Unusual noises: If you hear growling, screeching, or clattering noises coming from your AC unit, it could be a sign of electrical failures in the compressor.
• Whining noise: A whining AC compressor often sounds like a high-pitched squeal or shrill. You’ll usually hear it when you switch on the AC or when the car accelerates.
• Buzzing sound: A buzzing sound is a good indicator that your AC compressor may be damaged. You will notice this sound as soon as you turn on the car AC. The common cause of such a problem is normally excess refrigerant or leaky refrigerant.
• Vibrations: If the condenser unit is vibrating, it could be a sign of a faulty compressor.

What causes a compressor failure car?

There are several reasons why an AC compressor in a car might fail, including:

• Lack of refrigerant: A lack of refrigerant can cause the compressor to overheat and fail.
• Clogs: Clogs in the valves, filters, or condensers can cause a loss of pressure and lead to compressor failure.
• Electrical problems: Electrical problems, such as a failed O-ring seal causing a Freon leak or a clogged expansion tube, can cause compressor failure.
• Dirty filters: Dirty or worn HVAC or cabin air filters can cause bad odors and damage to the AC system.
• Broken parts: Broken parts, such as the compressor, blower motor, condenser, or evaporator, can cause poor airflow and cooling.

How long does a compressor last in a car?

The lifespan of a car’s AC compressor can vary depending on several factors. The average lifespan of a car’s AC compressor is around 10-12 years or 150 to 200K miles. However, the lifespan can be greatly impacted by factors such as frequency of use, car age, and proper maintenance.

Can you drive with a broken ac compressor?

Yes, you can drive with a bad AC compressor, but it poses risks. It may damage other components, reduce fuel efficiency, impair visibility, and lead to engine issues. However, if the compressor’s pulley is damaged and affects the serpentine belt, a malfunctioning AC compressor won’t harm your engine. If you’re unsure about the status of your AC compressor, it’s best to get it inspected and repaired by a professional. Attempting to fix it yourself could lead to further damage and costly repairs.

What happens when a compressor goes bad in a car?

When an AC compressor goes bad in a car, it can no longer circulate refrigerant, which means that the AC system will not be able to cool down your car effectively. One of the first signs of a bad AC compressor is when your dashboard AC vent is no longer sending cold air inside the car. Other symptoms of a bad AC compressor include loud noise from the AC compressor, moisture leak, stiff or non-moving compressor clutch, tripping circuit breaker, and broken suction lines. A whining AC compressor often sounds like a high-pitched squeal or shrill, and a buzzing sound is a good indicator that your AC compressor may be damaged. If you suspect that your AC compressor is faulty, it’s best to get it inspected and repaired by a professional. Attempting to fix it yourself could lead to further damage and costly repairs.

Can you fix a leaking ac compressor?

If you suspect a refrigerant leak in your air conditioner, the worst thing you can do to fix the problem is adding more refrigerant or Freon. If the leak isn’t sealed before adding more coolant, you will be faced with the same problem in no time. The first signs of a leaking air conditioning compressor can be recognized by the following: A/C takes more time than usual to cool the building, electric bill is higher than usual, warm air is coming from the supply vent, noticeable buildup of ice on the copper refrigerant lines, hissing or bubbling noises coming from the compressor. To fix a leaking air conditioning compressor, you can call a qualified technician to come by for a diagnostic check. Attempting to fix it yourself could lead to further damage and costly repairs.

How to tell if a car ac compressor is leaking?

If you suspect that your car’s AC compressor is leaking, here are some signs to look out for:

1. Hissing sound: A hissing sound coming from the engine compartment could indicate a refrigerant leak.
2. Decreased cooling performance: If your car’s AC is not cooling as well as it used to, it could be due to a refrigerant leak caused by a faulty compressor.
3. Increased fuel consumption: A refrigerant leak can cause your car’s AC system to work harder, which can lead to increased fuel consumption.
4. Refrigerant leaks: If you see refrigerant leaks around the compressor, it could be a sign of a bad compressor.