AC compressor low oil symptoms

The purpose of AC compressor oil is to keep all parts lubricated and help cool the various moving parts in the compressor.

In addition, the oil film protects the rubber seals -in the refrigerant lines and at joints/connections- greatly reducing the volume of refrigerant that leaks out.

As a result, an AC compressor can fail to cool air or have all kinds of problems if it doesn’t have enough oil.

The best way to prevent this issue is to keep an eye on the AC compressor low oil symptoms and to act when you notice signs of declining oil levels.

Below we explain all the common AC compressor low oil symptoms to help you learn when it needs an oil refill.

AC compressor low oil symptoms

There are a number of telltale signs that your AC compressors is running low on oil….

1.     Unusual Humming Noises

One of the earliest signs that the AC compressor is operating with an insufficient oil amount is the emergence of humming noises from your air-conditioning system.

At the same time, you may notice that the compressor has suddenly become hard to start.

Okay, the sound may indicate a failing starting capacitor but in most cases, a difficult-to-start compressor that simultaneously makes humming noises turns out to be low on oil.

We, therefore, recommend that you pay close attention if your AC system starts to make the weird humming noises because it may eventually stop functioning.

2. Seized AC Compressor

The characteristic of a seized compressor is often an indication of loss of lubrication meaning the compressor is starved for oil.

You see, oil circulates alongside the refrigerant so the AC compressor may run dry and finally seize when the system has a refrigerant leak at some place (allowing the two fluids to escape).

While there could be a hidden leak point somewhere, hoses, hose-pipe connections (flange gaskets and O-rings), the condenser, evaporator, or the AC compressor shaft seal itself are the most notorious leak points.

In this case, you should search for the actual leak (with the help of your electronic leak detector/dye if not easily visible) and mend it before adding more fluid.

3. Other AC compressor low oil symptoms

A desired effect of satisfactory lubrication is the lowering of the friction between load-bearing surfaces.

By minimizing or eliminating the abrasion, the system can run at maximum efficiency while extending the life of these components.

That being so, a reduction or complete loss of oil will lead to directly opposite results. 

For instance:

  • All bearing and rods inside the compressor will either be worn/scored.
  • The crankshaft will also be uniformly scored.
  • Rods might be broken if the compressor is seizing up.

One thing that could be causing the uniform wearing is the refrigerant’s flow being too low meaning that it cannot return oil as quickly as it’s being pumped out since there’s very little or zero oil in the crankcase.

What to do if none of the AC compressor low oil symptoms shows up

You can check for the oil levels physically if you haven’t observed any of these symptoms and your gut feeling tells you that the AC compressor could be short of oil

How to check oil in AC compressor

Run the following procedure to check if the remaining lubricant amount is safe…

  1. Connect a reclaimer machine to both the high side and low side valves on the compressor.

Note: For starters, you should look at the reclaimer machine as just a device that you’ll use to ease the traditionally strong pressure in the AC compressor and “capture” the Freon- you don’t want it to escape into the environment.

  • Turn the machine on.
  • Look for both the low and high side valves on the machine and turn each “on”.
  • Locate the button labeled “reclaim” on the machine and depress it. The machine ought to run until the gauges labeled for the low and high valves read 0 implying that the Freon has been captured from the AC compressor.

Note: The Freon is stored in a tank integrated into your reclaimer machine as you will need it when refilling your AC compressor later

  • Turn off the low and high valves on the machine (The reclaimer machine gauges should still be showing 0).
  • Disconnect the machine lines from your AC compressor.
  • Pull the AC compressor from the car.

Tip: Keep your bolts organized together- you don’t want to lose them.

  • Open its drain valve and empty the oil into any container that measures liquid ounces. 
  • Compare the readings to the recommended amount for your AC compressor. The unit may be oil deficient if the drained oil is less than required.
  • Proceed to fill your AC compressor with the right amount of oil as per the instructions then reinstall the replenished AC compressor in the vehicle.
  • Now recharge the Freon appropriately (again using your reclaimer machine).

Additional tips

  • The two pressure valves -on the AC compressor- are usually sealed and you have to open them using the valves on the reclaimer machine.
  • You can rent a reclaimer machine from auto repair shops since they can be quite expensive to purchase.
  • The best way to tell you have succeeded in refilling your air conditioning system is testing if it’s able to blow cool air properly after reinstalling the compressor.

Final Words

If you have a leakage in the AC system, it’s practical to first fix the leak before thinking of ways to deal with the AC compressor oil needs.

And when it comes to refilling the oil, you need to check the AC compressor specifications to be sure of the amount of oil that is needed (adding too much oil is also harmful to the compressor).

Besides, you’re to add the precise oil brand recommended by the manufacturer (check the owner’s manual or search for information about your exact AC compressor).

The last thing you require to always keep in mind is that you should evacuate the whole system before adding oil. 

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