Air Conditioner Compressor Replacement

The air conditioner compressor is the main component of any vehicle occupant cooling and comfort control system. This component is basically a refrigerant pump driven by the engine via a serpentine belt or on electric and hybrid vehicles a small electric motor mounted inside the unit.

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 or they will suffer a mechanical failure, either way they must be repaired. Though this job might be intimidating for some, the repair in the video is one of the most difficult in the industry which I performed myself. Though appearances may differ, the process similar for most vehicles.

In the guide below I will discuss this procedure in detail while giving you tips and information the video below may have missed. Enjoy the show and then travel through the information below to gain additional knowledge.

This job is typically done in under three hours but can save you hundreds of dollars with the satisfaction you did the it yourself, so lets get started!

Tools and Supplies Needed

  • Air Conditioner Compressor
  • Tool set
  • Shop towels
  • Protective eye wear
  • Work gloves
  • Air conditioner gauge set
  • AC vacuum pump
  • R134a refrigerant supply
If any of these items are needed they can be purchased at Amazon or a local auto parts store.

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

Step 1

Air conditioner systems are filled with refrigerant under pressure, we must check to see if any refrigerant is left in the system before you disassemble, this is done using an a/c gauge set. If the system is "flat" and all the refrigerant has escaped, continue with this guide. If the system is still has refrigerant present it must be discharged before the repair. Checking the pressure or refrigerant level is done through the low side service port.

The low side pressure port is located on the larger of the two refrigerant tubes. To locate this port follow the larger of the two refrigerant lines which connect from the evaporator core (from firewall) to the rear of the compressor. Remove the low side port cap and attach the gauge set connector valve to check system pressure. Learn more

Step 2

Once the refrigerant has been removed, loosen the negative cable from the battery terminal to disconnect, this will avoid accidental short circuits while the work is being done. (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 3

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.

Step 4

The serpentine belt must be removed which drives the compressor except for hybrid and electric cars. Using a wrench or socket, release tension on the belt by applying opposing force on the tensioner, this will loosen the belts grip on the pulleys so it can be removed. once the belt is off it's a good time to inspect and replace it if worn, glazed or cracked. This operation is easier on rear wheel drive engine configurations than front wheel drive vehicles.


Step 5

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 remove additional accessories such as an alternator which can be done by loosening and removing wiring connectors and mounting bolts.

Step 6

Once these obstructing accessories have been removed, locate the electrical connector located on the front or rear of the compressor. This connector 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. If this connector cannot be seen or its too difficult to remove you can do so once the mounting bolts have been removed.

Step 7

Once the refrigerant has been released or recovered and the low side gauge pressure reading is at zero, locate and remove high and low side refrigerant line mounting bolts or flare nuts depending on 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.

Step 8

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 small amount of refrigerant (pressure) maybe released as well, complete this step by removing both tube fittings.

Step 9

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, if so, use a universal joint socket or small wrench to aid in the removal. Always leave at least one bolt connected to the bracket or block but loose, to hold the unit in place.

Step 10

Next, grasp the unit while removing the last mounting bolt, the compressor is heavy and a little 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 it's 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 11

Once the unit has been removed, turn the pulley or clutch to determine it's condition by checking for rough movement or grinding noises, if present this sometimes means 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 12

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.

Step 13

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

Step 14

Though the system has peg oil throughout it's internal workings which is usually including in the 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, read the installation instructions for more information which are supplied with the unit.

Step 15

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 help them hold the refrigerant. 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.

Step 16

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 seal 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.

Step 17

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 18

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 it's mounts or engine block.

Step 19

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.

Step 20

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.

Step 21

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

Step 22

Reinstall any accessories such as the alternator by gently lowering the unit into the engine bay while installing the mounting bolts and electrical connectors.

Step 23

While holding back the serpentine belt tensioner, reinstall the belt back 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, make sure all belt pulleys are properly seated against the belt.

Step 24

Once completed 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 be vacuumed down and recharged, never simply fill the system with refrigerant because moisture is present inside the system due to the normal atmosphere once it was opened and will cause the compressor to fail prematurely. Using an a/c gauge set and vacuum pump proceed in this operation of moisture removal and system recharge.

Also See: Air Conditioner Troubleshooting An air conditioner compressor can fail either by leakage or by an internal mechanical problem which is usually accompanied by abnormal noises while in operation. High mileage car's trucks and SUV's are prone to failure due to usage. 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