How to Replace an Air Conditioner Compressor

Need to replace your cars air conditioner compressor? We are a team of ASE certified mechanics that have created this guide so you can save money and get the satisfaction of doing the job yourself or see what you are paying for when taking your car is for repairs. Let's jump right in!

What Goes Wrong?

Responsible for receiving spent (low pressure) r134a refrigerant and compressing it into the high pressure gas these units are prone to failure which usually happens in one of two ways. Either they can leak refrigerant from the body or the front seal or they will suffer a mechanical failure and create a rattling noise when switched on or just lock up altogether. Either way the compressor must be replaced.

Getting Started

Though this job might be intimidating for some, it's not too bad once you get comfortable by seeing it done first. Its like Bob and Ken (2CarPros) always say;" it's just nut and bolts". This job is typically done in under four hours and can save you up to a thousand dollars and have the satisfaction that you did it yourself.

Though appearances may differ the process very similar for most vehicles. Enjoy the video and then travel through the information below to gain additional knowledge.

You will need replacement parts and an air conditioner gauge set and vacuum pump which you can get from Amazon for a little over a hundred bucks. Then you will have them for the next time any air conditioner work needs to be done for family or friends.

Before work begins park the vehicle on a flat surface with the emergency brake on, engine off while wearing protective eye wear and gloves.

Before Beginning

When doing any a/c repair is a good idea to know how the air conditioner system works so you may have a better understating of the system operation.

Before opening the system up we must check to see if any refrigerant is left inside before disassembly.

Learn more: Checking refrigerant levels

Most of the time when a compressor needs replacement its because of a leak so the system will be flat in which case you can continue with this guide.

Disconnect the negative side of the battery to avoid electrical short when working around the engine. (Note: If the radio is being used, record it's presets as they will need to be re-entered after the battery is reconnected.)

Step 1: Remove Air Intake and Accessories

Unbolt and remove any tubing or hoses to gain access to the serpentine belt for removal. This tubing is used for emissions and air filter intake proposes and is usually easily removed by undoing minor bolts or screws. Next, the serpentine belt must be removed which drives the compressor except for hybrid and electric cars.

Step 2: Removing the Compressor

While some compressors are in plain sight others can be buried beneath a layer of brackets and accessories such as an alternator or power steering pump. To gain access to the compressor remove additional accessories such as an alternator. This can be done by loosening and removing wiring connectors and mounting bolts.

Once these obstructing accessories have been removed locate the electrical connector on the front or rear of the compressor. This wiring is uses to energize the engagement coil if it's located in the front or the internal control valve if located in the rear. Use a small pick or screwdriver to release the electrical connector safety. If this connector cannot be seen or its too difficult to remove you can do so once the mounting bolts have been removed to the compressor.

Locate and remove the high and low side refrigerant line mounting bolts or flare nuts depending on the manufacturer design. Again on some models this step may need to be performed after the mounting bolts have been removed and the unit is loose.

After the bolts have been removed firmly grasp and wiggle the line bulkhead of each refrigerant line to slowly pull upward and disconnect. There is an O ring seal which can make a tight fit and a small amount of refrigerant (pressure) maybe released as well. Complete this step by removing both high and low side fittings.

Once all wiring harness connectors and refrigerant lines have been removed locate and remove lower and upper mounting bolts. These bolts can consist of long and short bolts which sometime can be obscure and difficult to get to and if so use a universal joint socket or small wrench to aid in the removal. Always leave at least one loose bolt connected to the bracket or block to hold the unit in place.

Grasp the unit while removing the last mounting bolt the compressor is a little heavy and a bit awkward to hold so be careful it doesn't fall and cause damage to the unit or yourself. Once completely loose remove it from the engine bay. This can take some work and sometimes you must move the engine a tiny bit in its mounts or possibly even loosen the engine mounts and use a jack under the oil pan to help lift it slightly. Other times a radiator or cooling fan shroud must be removed as well.

Step 3: Checking the Old Compressor for Damage

Once the unit has been removed turn the pulley or clutch to determine its condition by checking for rough movement or grinding noises. If present this sometimes can mean the system is contaminated with foreign metal debris from the failed unit which can plug the orifice tube or expansion valve. In these cases the system must be flushed by using an a/c system flush kit which can be purchase from Amazon or the local parts store.

If the system is completely plugged its best to replace the expansion valve or orifice tube along with the receiver dryer or accumulator depending on the system design. Inspect for obvious contamination by looking inside the refrigerant lines or intake and exhaust ports for metal particles.

Step 4: Preparing the New Compressor

Compare the new compressor to the old unit to ensure a proper installation. Sometimes the replacement unit can look slightly different due to updates and slight design variations. The one thing to look for is the configuration of the refrigerant ports on both the intake and exhaust sides. Also, check the belt pulley by counting the number of ribs which the belt must ride on also the outside diameter must be correct.

When installing the new compressor into the engine bay it's a good idea to transfer some of the mounting bolts from the old unit or before lower it into the engine bay this will help for easier installation.

Though the system has peg oil throughout its internal workings and is usually including in the new compressor it's a good idea to add a slight amount (1/2 ounce) of compressor oil to ensure proper lubrication before installation, then reinstall dust caps. Some units have oil already installed be sure to read the installation instructions for more information which is supplied with the replacement unit.

Step 5: Replacing the O Ring Seals

O rings are used to seal the high and low side lines to the compressor housing. These sealing surfaces must be clean and free from dirt or damage to keep them from leaking. Use a small screwdriver or pick to carefully remove the old O ring seals from both the high and low side lines without scoring the sealing surface where the O ring sits, this will ensure a proper seal.

Match the old O rings to the new ones to ensure a proper seal. Keep an eye on the thickness because some O rings can be smaller in diameter then others. It's a good idea not to reuse the old seals because they become flattened over time due to pressure and heat and may leak which would cause the job to be redone which means vacuuming down and recharging the system.

After cleaning the fitting thoroughly install a new O ring seal on each the low and high side fittings. Once installed apply a thin layer of peg oil over the O ring to help the installation without damaging or cutting the new seal, repeat this process for each line.

Step 6: Installing the New Compressor

Clear any hoses or lines while gently lowering the new unit into the engine bay. Hand thread in the mounting bolts which will hold the unit into its mounts or engine block.

Once all mounting bolts have been hand threaded in use a wrench or socket to tighten the mounting bolts evenly in a cross pattern. This will help to not distort the housing which can cause premature failure.

Remove the port dust covers and install both high and low side refrigerant lines with the mounting bolts and then tighten. These bolts don't need to be extremely tight just snug enough to not come loose and seal against the housing.

Once all the mounting bolts are tight make sure the electrical connector is clean before reconnecting it to the engagement coil or refrigerant control valve.

Reinstall any accessories such as the alternator by gently lowering them into the engine bay while installing the mounting bolts and electrical connectors. While holding back the serpentine belt tensioner, reinstall the belt into place. Once completed double check the alignment of the belt by inspecting the pulleys of each accessory and drive pulley located on the engine crankshaft.

Step 7: Finish Reassembly

Reinstall any tubes or hoses removed in the replacement process continue by tightening all bolts, screws, clips or brackets previously removed. Now the system is ready to have a vacuum down and recharge service performed. Never simply fill the system with refrigerant because moisture is present inside the system due to the normal atmosphere that entered once the system was opened. This can cause the compressor to fail prematurely and the system will not work as well.

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Helpful Tip

If the vehicle is used in colder weather and the system is not used much it's a good idea to turn the system on occasionally to help move the oil around the system which will help lubricate the seals and help the compressor last longer.

Need more information about this repair? Please visit our forum where thousands of air conditioner compressor questions have been answered by our mechanics.

Article first published