How to Fix a Buick AC Compressor

There was a time when you had to special order your Buick with air conditioning because it wasn't a standard feature in the basic cars, but nowadays you can't get a new car without air conditioning even if you wanted to - and why would you? A/C is great on those hot summer days.

Of course, if your AC isn't working, it can be pretty noticeable. While there can be lots of potential causes for A/C problems, we're going to focus on when your compressor goes bad. Here's what you need to know.

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Compressor Issues

The compressor is responsible for the operation of the air conditioner by sending the refrigerant into the system. It is a mechanical part that works hard and runs hot. It also has to withstand several hundred pounds of pressure per square inch. The compressor is lubricated in order to keep all those moving parts operating friction-free. If the lubricant leaks out or is contaminated, your compressor is not going to last.

Compressor failure will result in a loss of cooling. It may have seized up, which stops it from turning when the clutch is engaged. It's also possible the belt may have broken. It will make a squealing sound when it's not operating.

A loss of fluid is by far the most common reason that a compressor fails. A refrigerant leak can cause both refrigerant and oil to escape the HVAC system. Generally, a leak is at the connections of hoses, gaskets and pipe connections that consist of o-rings or flange gaskets. Leaks can also be found at the condenser, evaporator or the shaft seal to the compressor. You can use a leak detector for electronics to find the leak.

Additionally, if there is any restriction within the air conditioning system, the compressor may be starved for oil, which travels through it with the refrigerant. The expansion valve or the orifice tube may be blocked. That can cause the compressor to seize up due to being dry.

A compressor that is leaking or making noise will need to be replaced whether it is still turning or not. If the sound is metallic in nature, it usually means that the compressor is going to fail. There can be loud noises that may mean that there is air in the system. If it is air, then vacuum purge the entire system to get rid of the air and recharge with refrigerant.

You will need a new compressor if there is a leak or inadequate pressure because the reed valves are bad. It may also have worn piston rings or scored cylinders. If your compressor has internal issues, it will never be able to get the proper pressure needed in order to run the system. You can use a gauge set for air conditioners to diagnose this issue.

Keep in mind that an air conditioner that is not running cool enough may not be the compressor’s fault, so do not replace it until you have looked at the other causes. You may be low on refrigerant. There may be too much oil in the system, or the air is contaminated. There may be a clogged condenser or some other plugged part or a faulty cooling fan.

The compressor in your Buick is operated by sensors if you have the automatic temperature control system. This system has a pressure transducer that will shut the compressor off if there is too much refrigerant pressure. It can also turn the compressor off if it's running too hot or the belt slips.

Clutch Issues

The compressor is turned by the magnetic clutch any time that it's engaged. It may not be energized if there is a bad relay, wiring issue, blown fuse or is somehow defective. A clutch that does not cycle off and on when the air conditioner is turned on can be jumped by using a jumper wire and the battery. If you can get the clutch to jump start, your problem may be in the power supply. Use your wiring diagram and work backwards towards the battery and search for the voltage leak.

Your system may be installed with a low-pressure cutout that will keep the clutch from engaging if the pressure in the system drops too low. This is a preventative measure to protect the integrity of the compressor. When the clutch is not engaging, take a look at the cutout switch or the refrigerant charge. You also should look at the clutch air gap for inadequate clearance. If this is not correct, the clutch can slip and burn. The spec for this is in a Buick service manual and will give you adjustment instructions. Usually, the clutch is set for 0.015 to 0.040 inch press fit clearance.

Defective Compressor

While it is uncommon for the compressor to actually fail due to manufacturing defects, it can happen, but the odds are very slight. Generally, a compressor fails due to a lack of oil, contamination of the system, air within the system or a user error like wrong lubricant, inadequate lubrication or non-approved flushes. The most common cause of repeated compressor failure is left over debris from a previous compressor.

You need to use the recommended lubrication for the specific compressor you have in your Buick, especially if you have a rotary vane or scroll-type compressor. Your replacement compressor may not come with lubrication from the factory, so you need to remove any shipping oil contained in it before you install it. Use the instructions that came with the replacement compressor to ensure that you have the right lubrication.

Remove all oil from the system before you add new oil. This keeps cross-contamination down and lowers the risk of overcharging. Check your Buick OEM oil capacity for the correct amount.

Flushing

If you have a compressor failure, you may have metallic pieces from the compressor throughout your air conditioning system. This debris may cause blockages in the tubes at the condenser. It can also travel to the expansion valve or orifice tube. It can even be in the suction tube. If you do not flush the system, you run the risk of the old debris causing your new compressor to fail.

Flush the hose and the condenser. You may consider replacing the condenser, so that you know the debris is completely gone. A parallel flue condenser can be hard to clean. However, you can clean a serpentine tube and fin condenser successfully. The newer condensers have small tubes that are difficult to clean, so you might as well just replace the condenser rather than run the risk of ruining a new compressor.

After you have flushed the system put an in-line filter in to trap debris. Put this after the condenser. It will keep debris from going to the orifice tube. Additionally, add a filter screen within the suction hose located at the inlet to the compressor. This will also keep debris from getting to the new compressor.

Flushing gets rid of the old oil and ensures that you will start with the right amount of oil. It's better than guessing how much oil has been removed. This way, you can use the factory recommended amount of oil.

If you don't have the right amount of oil, you run the risk of reduced compression and failure of the compressor. When you have too much oil, you can get obstructions in the refrigerant flow and poor performance.

When you replace a compressor, you want to replace the accumulator, orifice tube, receiver/dryer and expansion valve. The accumulator has a desiccant in it and the expansion valve or orifice tube has a very small hole that is easily clogged.

Evacuation and Recharge

Once you get the compressor installed and reconnected, you need to evacuate the system. Use a vacuum pump to take all the air and moisture out. If you do not remove it, you will have less ability to cool along with an accumulation of acids and sludge from the reaction of moisture and refrigerant oil. The moisture can also plug or freeze the expansion valve. This can cause a blockage.

Use a pump that has high vacuum capabilityof at least 29 inches Hg of vacuum. This vacuum causes any leftover moisture to boil and then evaporate.

Use a Thermistor Vacuum Gauge to monitor the process. You do not want any moisture left in the system at all, so you need to be able to ensure that it is completely evacuated.

When you are finished, close all the valves and turn off the vacuum pump. You may be able to see a rise in pressure on the Thermistor Vacuum Gauge. Continue to take vacuum out until there is a stable reading below 700 microns for three minutes.

You can reduce the time it takes to completely evacuate the system by preconditioning your evaporator before you hook up the vacuum pump. In order to do this, you need to raise the temperature by running the engine with the heater turned to HOT using the RECIRC mode. Close all your doors and windows and set the blower fan to High. After the engine temperature reaches the normal temperature, you can turn it off and start your evacuation.

If you cannot keep a steady vacuum, you may have a leak in your air conditioning system or equipment connection. Do all of your leak testing before you evacuate the system because you may not find a small leak. Vacuum pressure can cause seals or o-rings that normally leak to stop leaking as long as there is pressure.

When you have finished, recharge the system with the proper amount of refrigerant and oil. Make sure that you do not overcharge the system or overfill the oil, and also make sure that the cooling is operating properly and the compressor is running.

If you run into any trouble during the diagnosis or installation, then consult your local Buick dealership for assistance.