How to Replace Your Vehicle Air Conditioner Compressor

How to Replace Your Vehicle Air Conditioner Compressor

There are many possible causes of air conditioner (A/C) compressor failures, and it can happen even on the most expensive, high-end cars. However, in all cases of A/C compressor failure, it is crucial to determine the cause, and to take suitable corrective action to prevent the replacement compressor failing for the same reason. The most common causes of compressor failure are lack of lubrication because of the loss of refrigerant, and the presence of moisture in the refrigerant that causes corrosion.

Replacing a compressor is no simple matter, but by following the instructions in your repair manual it s certainly possible, but the real problems start once the actual compressor has been bolted onto the engine. For this reason, we have compiled a list of ten steps to follow to prevent subsequent failure of the replacement compressor, so read on, and we will explain the steps in turn.

1.) Do NOT vent residual refrigerant into the atmosphere, since this illegal in most jurisdictions. Identify the refrigerant, and only use suitable equipment to evacuate the system in accordance with local laws, regulations, and statutes.

2.) Follow the instructions in the repair manual to remove the old compressor. Use the instructions that came with the replacement to identify all brackets, switches, valves, and other equipment that must be transferred to the replacement. Do all of this before fitting the replacement compressor, since you may not have sufficient working room once the replacement compressor is attached to the engine.

3.) Only use approved solvents and cleaners to clean, or flush A/C components that are to be re-used. However, it is important to do this in a dust-free environment to ensure that no solid particulate matter is transferred into the system during reassembly. Also make absolutely sure that no solvent is present on any component- use dry, filtered compressed air to blow dries all components that are to be re-used.

Always replace the accumulator, also known as the “dryer”, and all expansion devices, including the orifice tube, or the expansion valve that does the same thing, but is used on some systems instead of an orifice tube. Use the repair manual to identify these components, and make sure you replace them only with their exact equivalents.

4.) Install the replacement compressor, following the steps outlined in the repair manual, and check to ensure proper tension and alignment of the drive belt. Do however, NOT modify anything if the belt is misaligned, or not tensioned correctly. If this happens, you most likely have the wrong compressor, so double check all measurements and features of the replacement compressor against the existing unit to ensure they are identical in all respects- before you attach it to the engine.

5.) At this point, it is a good idea to install a suitable inline filter near the compressor inlet to prevent introducing solid contaminants into compressor that will almost certainly destroy the replacement compressor as well. Use the instructions that came with the filter to ensure you install it correctly.

6.) If the replacement compressor is supplied without lubricant, consult the instructions to ensure the correct amount of lubricant is added, and only use the lubricant that came with the replacement, since lubricants, refrigerants, and compressors are not always compatible. Do NOT use any liquid, refrigerant or other items that are not specifically recommended for your replacement compressor, or existing A/C system.

7.) Only use approved equipment during the next stages of the procedure. If you do not have access to the correct equipment, take the car to a specialist A/C fitment centre. However, if you do have the correct equipment, follow the instructions that came with the replacement compressor to evacuate the system to a minimum vacuum of 29 inches Hg.

The A/C system must maintain this vacuum for at least one hour; if it does not, there is a leak in the system, and the refrigerant will escape soon after recharging. Locate the leak, and repair it BEFORE charging the system with refrigerant.

8.) Again using only approved equipment, follow the instruction in the manual to recharge the system with the EXACT amount of refrigerant. One way of doing this is to place the container holding the refrigerant on a scale that can measure grams, and to monitor the scale until the EXACT charge is reached.

This is vitally important because a few more grams of refrigerant will NOT make the system work better. What WILL happen however is that the system may freeze up because of the higher charge, which will seriously affect the performance of the entire A/C system? Moreover, incorrect amounts of re3frigerant are one of the leading cases of system failure, so make absolutely sure you charge the system to within one gram of the recommended charge.

9.) Recharge your air conditioning system using the recommended Freon only. Use a scale, metering device or buy different sized cans to ensure the proper amount of refrigerant is installed, specified by the vehicle manufacturer.

10.) If you are satisfied that nothing has been left undone, and that the refrigerant charge is correct, start the engine, turn on the A/C system, and check that it performs satisfactory. Also check that there are no mechanical noises of any kind, except for the “clacking” sound made by the compressor clutch as the system cycles. Any other kind of noise is a bad sign, and the system should not be used until the source of the noise has been identified and the problem corrected.

Allow the system to operate for at least 30 minutes, and check that the condenser fan(s) work, and that the system does not freeze up. However, if all instructions were followed to the letter, there should not be a problem.


You have just successfully completed a major task, but not only that, you have saved several hundred dollars by doing it yourself!

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