Friday, May 17, 2024

How To Test Car Ac Compressor

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What Causes Ac Compressor Failure

How To Test Clutch On Your Car AC Compressor | Using Simple DIY Lead Wires, Multimeter & Power Probe

Before you know how to tell if a car AC compressor is bad or not, you have to know the reason behind the failure of AC compressors.

1. In most cases, dirty coils are the reason for the AC compressor failure. If the compressor gets overheat, it may stop working.2. If the refrigerant lines are blocked or if they get damaged in any way, the AC compressor will not work at all.3. On the other hand, if there is excessive refrigerant then also the compressor will not be effective.4. Electric failure can buildup acids and ruin the compressor.5. If the oil lubricant is not ample then the compressor will be unworkable.

What Does A Compressor Do

The compressor is a part of the high pressure side of the A/C system, which converts refrigerant gas to liquid as it passes through the condenser.

The compressor does exactly what it sounds like, it compresses the refrigerant gas which then makes it very hot. This is passed onto the condenser which cools the gas, converts it to liquid and circulates it to the receiver drier and expansion valve.

From here it enters the evaporator, where it is exposed to warmth from air in the cabin and turns back to gas. As the name suggests, it evaporates and as a result becomes very cold. This cold is conducted through the metal tubes and fins of the evaporator to deliver cool, dry air into the cabin as dictated by the blower fan.

As you can probably tell by now, the compressor is an essential part of this process.

How To Test Car Ac Compressor Step : Examine The Power Supply On The Ac Compressors Clutch

Attach the negative multimeter probe lead on the negative terminal of your vehicles battery to understand whether there is any power flow on terminals 2 and 3. If no voltage reading is being displayed on the multimeter, examine the fuses and wiring to the relay.

If there is power, connect the negative probe lead on terminal 3 and the positive probe lead on terminal 4 and check the multimeters battery voltage display. In case there is no reading, the PCM may have a problem and not produce ground to the control relay coil.

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Insufficient Refrigerant In Compressor

Check if the pressure gauge of the high-pressure side recognizes too low a pressure. This will tell you if there is too little coolant in the compressor. You can inspect your vehicles AC manual for the correct pressure level.

Repair kits made for charging refrigerants are available in the market, and they come with instructions on how to do it.

How To Test Car Ac Compressor Step : Check The Ac Compressor For Damages

How much does Car AC Compressor Replacement cost? Get an ...

Before examining the AC compressor, make sure you turn off the energy circuit to the conditioning unit. This vital step will protect you from getting electrocuted when conducting this test. Switch off the AC compressors power circuit along with any other switch you see around it.

Afterward, unscrew the faceplates and remove them from the AC unit, and this will allow you access to the internal elements, particularly the ventilation holes, among other internal pieces. Remove the power access panel and inspect how the wires have been linked to the air conditioning unit once you are done. Moreover, you should look around for burnt terminals within the system.

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How To Test Car Ac Compressor Step : Check For Continuity At All The Pressure Switches

Set the multimeter to ohms before placing a 1-meter lead on terminal five located on the low-pressure switch. Connect the other to terminal seven on the switch. The refrigerant is okay if the switch is shut, and you see the right readings. But if the pressure is dangerously low, the switch will open, and you might get incorrect reading values between the two terminals.

Conduct the same process on the maximum pressure switch, keeping the multimeter on an ohm setting. Only this time have a multimeter probe lead connecting to terminal eight and terminal six.

If the switch is shut off, understand that the refrigerants pressure is perfect, as the multimeters reading value will be shown. On the other hand, if the pressure is too high, the switch will open, and the reading will be infinite around five and seven. Take this as a sign that there is a major problem with your cars AC compressor that has to be repaired as soon as possible.

How To Diagnose Car Ac Compressor

After noticing one or more signs of a bad AC compressor above, you might want to know how to test a car ac compressor so you wont end up replacing a well-functioning compressor unit. Here are a few easy and straightforward ways to diagnose your car ac compressor.

  • Check temperature fluctuations
  • Check physical damage and oil leaks
  • Check if the clutch rotates freely
  • Listen for squealing and skipping noise
  • Check refrigerant leaks

Step 1. Check temperature fluctuations: If you are getting warm air when your AC system is engaged, chances are you have a lousy or failing ac compressor. If the AC is still working, check if the AC temp fluctuates if it does, its an indication of a failing ac compressor.

Step 2. Check physical damage and oil leaks: Visually inspect your vehicles ac compressor for rust, physical damage, and oil leaks. These signs indicate a lousy or failing car ac compressor. Compressors with oil leaks will not work optimally and can even cause premature failure. Low oil in ac compressor resulting from compressor leak will cause friction leading to erratic temperature when the air conditioning system engages.

Step 3. Check if the clutch rotates freely: Inspect the AC compressor clutch and ensure its not making a grinding noise when turning or hard to turn. The clutch should turn freely. A lousy clutch can damage your entire compressor unit.

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How Do I Test My Car Ac Compressor

A/C compressor Test. Compression ratio test.The A/C compressor is considered the heart of the refrigeration system. The term that best describes a compressor is vapor pump, because it actually increases suction pressure level to the discharge pressure level.Compression ratio is the technical expression for pressure difference it is the high-side absolute pressure divided by the low-side absolute pressure. Absolute pressures rather than gauge pressures are used when figuring compression ratio in order to keep the calculated compression ratio from becoming a negative number. Absolute pressures keep compression ratios positive and meaningful.Compression ratios are used to compare pumping conditions for a compressor. When compression ratios become too high, the refrigerant gas temperature leaving the compressor rises to the point that oil for lubrication may become overheated. Overheated oil may turn to carbon and create acid in the system.To check a/c compressor compression ratio, note on paper the low and high side gauge readings and add atmospheric pressure to both readings. Divide the high side reading by the low side reading .The result should be between 6.5:1 and 7.5:1. A compression ratio of 8:1 or higher may cause compressor failure.If the A/C system operating pressures of your car gives you out of range values

A/c Compressor Bench Test

How to check if AC compressor is bad

PostsThe clutch is engaging when you hear the click….Compressing?? that depends on if you turn it will it compress gas.If you turn it fast enough it will always compress to a degree……even if it is completely worn out…..But if it is turning slowly will it compress…..I guess if there is a large nut that holds the shaft, you could apply your 12v to engage the clutch and then use a drill with a socket on the end to turn that nut thereby spinning the compressor to see if you get any kind of suction or compression out of it. The Black round type is are only $250 for a new one at this OEM GM supply house I know of in Huntington Beach.dammit, see they are a dealer supply… they are hard to find on purposebut they sell to the public?Heimlich2010ok im trying to diagnose some A/c stuff before i put it all back together. im trying to figure out if the compressor works. if i apply 12 volts to the a/c compressor plug the a/c compressor makes a click noise. if i look at it when i apply 12v the clutch sucks in maybe 1/4 inch to 1/2 inch. does this mean my compressor at least works? i know when its running properly the a/c clutch sucks all the way in but i assume when bench testing if it just moves a little it is good… can any one help me outpcolt94Posts

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Ac Accumulator / Drier

The Accumulator/Drier collects and absorbs moisture. Moisture is like poison to the internal system components and can damage the AC Compressor as well. Depending on your vehicle, you may have an accumulator or a receiver/drier.

Common Problems: Internal failure allowing desiccant material to enter the AC system. Like sugar in the gas tank, this stuff in the wrong places can cause major problems. Leaks can result in over-saturation of the desiccant material that can lead to compressor damage.

How To Replace The Car Ac Compressor

You already know how to test a car AC compressor, so now you may be interested in how to replace a faulty unit. You can save a few bucks by DIY-ing this repair, so why not? Only try to replace the AC compressor yourself if you have some experience handling car components and are confident. But before that, put on your latex gloves and a pair of safety glasses!

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How Does A Vehicles Air Conditioning System Work

Your air conditioning system comprises of five main components, including:


This is an essential component of a cars A/C as it pressurizes refrigerant to cool the air. Refrigerant is a gaseous substance used for cooling.

Furthermore, the compressor senses temperature changes inside and outside your car while controlling the temperature output.


Located at the front of the radiator, the condenser receives air from the compressor and works to reduce the temperature/pressure of hot gasses coming from the refrigerant.

Receiver or Dryer

A receiver or dryer works to separate gas from the liquid while taking away moisture. It has filters that protect the A/C from contaminants.

Thermal Expansion Valve

Located between the condenser and evaporator, it monitors the pressure and temperature in your A/C system before calculating the exact amount of refrigerant that can go safely into the evaporator for cooling.


Behind the dashboard, the evaporator is in charge of cooling the air with the refrigerant before the air is blown in your vehicles cabin.

How To Diagnose Car Ac Compressor Failure

How to check clutchless ac compressor
  • HowTo
  • How to Diagnose Car AC Compressor Failure

Air conditioning is something many people take for granted until it stops working. It can be annoying if during a hot day, you reach down to crank up your AC and all that comes out is hot air. More importantly a bad compressor can be dangerous. If your compressors bearing goes bad, your engine can seize due to the stuck compressor. If you are traveling at speed and the car shuts off, you no longer have power steering nor is your brake booster functioning. There are a few reasons your AC system might stop working and the central part of it is the AC Compressor. Here are a few ways to diagnose a car AC compressor failure.

Step 1:

If the air temperature does not cool when the AC system has engaged there is a good chance that there was an AC compressor failure. If the AC still works, check to see if the temperature fluctuates while the AC system is running.

Step 2:

Find you AC compressor and visually inspect it for rust, physical damage, oil leaks or paint damage. All of these are signs of a car AC compressor failure. With a lack of oil, the compressor will not function efficiently and will cause premature wear. The increased friction will also lead to erratic temperatures when the AC system is engaged.

Step 3:

Check your belts to ensure there is proper tension and the belts are not damaged. Cracked or splitting belts can cause further damage to your AC compressor. If they are bad, they should be replaced with a new compressor.

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Failure Of The Compressor To Turn On

If you notice that the air conditioning is not cooling your home to the temperature youve set and the fan inside your home is working properly, check your condensing unit outside your home. If you hear the fan running but the aircon compressor is not running, you have a problem. The compressor should be clearly audible over the fan.

If this is the problem, you may face a replace or repair choice. Failed compressors can be expensive to replace so how to know if the A/C compressor is bad is vital. If your system is aging and has been in operation for about 10 or 15 years, it might make more sense to invest in a new air conditioning system rather than a costly repair.

How To Test The Compressors Clutches

Step 1

Just open the hood of your vehicle, and find the air compressor. This is located on the upper left-hand side of the engine compartment.

Step 2

Now turn the air conditioner selector knob in your vehicle to an off position, and then start your engine.

Step 3

Now connect the voltage tester to the negative connection on your vehicles battery.

Step 4

Find the wires coming off of the ac compressor, and unplug them. Note that all of the wires should be connected with one wire feed. Then you can place the voltage tester on each of the three connections individually. Note that no activity should be noted on the voltage meter.

Now turn the air-conditioner selector knob to the on position. Then place the voltage tester on each of the three connections. Right now the middle connection should produce activity on the voltage tester, indicating the connection is hot. But if no activity is noted, then your air compressor clutch and wire should be replaced.

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Understanding The Ac System And Components

Your car’s air conditioning system works just like a refrigerator or your home air conditioning. The purpose of the system is to remove hot air from the inside of your vehicle. It consists of the following components:

Component 1: Compressor. The purpose of the compressor is to pressurize the air conditioning system and circulate the refrigerant. It’s located at the front of the engine and is typically driven by the main drive belt.

Component 2: Condenser. The condenser is located in the front of the radiator and is used to remove heat from the refrigerant.

Component 3: Evaporator. The evaporator is located inside the dash of the vehicle and is used to absorb heat from the interior of the car.

Component 4: Metering device. This is known as a metering tube or an expansion valve and can be located either under the dash or under the hood near the fire wall. Its purpose is to change the pressure in the air conditioning system from high pressure to low pressure.

Component 5: Hoses or lines. These consist of metal and rubber lines to carry the refrigerant.

Component 6: Refrigerant. Typically, all systems today contain R-134A refrigerant. This can be purchased over the counter at most auto parts stores. Older vehicles were built with R-12, which is no longer used because it contained high amounts of ozone depleting compounds. If you have a license and certification you can still purchase this, though most people opt to retrofit this system to the newer R-134A refrigerant.

How A Air Con Compressor Works


The air con pump is responsible for purifying the air in the car by cooling it down as well as reducing the humidity of it , the same way an air con system in buildings work. The air con pump is powered by the flywheel with a clutch that controls it. The pump brings in refrigerant gas and compresses it at such a high pressure it causes it to heat up. This heated gas is removed by sending it through the pipes and into the condenser at the front of the car which will then convert this gas into liquid from the cold air thats passing through it.

Next the liquid will pass through a reservoir which will dry it causing it to purify by removing moisture. Then it will be sent to the heat exchanger through another set of small pipes. The liquid will be extremely cold and will need heating and this is the responsibility of the heat exchanger. It heats up the liquid by sending warm gas over it before its taken by the air con compressor pump. This a cycle so once its reached the heat exchanger and pumped into the cabin of the car the air con pump will bring in more gas from the heat exchanger and the cycle will start once again.

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Unusual Car Ac Sounds

When your cars air conditioning system makes unusual noises, this often indicates an AC compressor problem. Unlike refrigerant leaks, this is a sign of a mechanical shift somewhere in your cars air conditioner. One of the most active parts within your vehicle AC system is the compressormaking it a likely culprit.

What Is A Vehicle Ac Compressor

Before we dive into the signs of an AC compressor failure, lets answer one of the most common questions we get from customers: What is an AC compressor? Your cars compressor pumps refrigerant through your AC system to provide your vehicle with cool, comfortable air. Without the refrigerant circulation, your car will be unable to cool the air it distributes through your cabinthus, leading to an AC system that produces warm air.

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