How to add oil to air conditioning compressor [step by step]

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Think of oil as the life’s blood of your AC compressor- it lubricates, removes heat, and helps in sealing (to prevent leaks).

As such, you cannot afford to have it run without the right amount of oil (here are the common AC compressor low oil symptoms).

Besides, some new compressors need to be added with oil prior to installation.


How to add oil to air conditioning compressor

This is not usually that hard and in fact, you should be done in about 4 major steps.

Here is a summary of the steps:

  • Remove the AC compressor.
  • Drain the old oil.
  • Add new oil.
  • Reinstall the compressor.

Preliminary step

Purchase the oil that your manufacturer recommends (Putting the wrong type oil in your AC compressor is likely to damage it).

How to add oil to air conditioning compressor – step by step

The first thing to do is remove the AC compressor.


Step 1: Locate the compressor and remove the protective cover

Remove the bolts mounting the AC compressor protective covering and take it off (use a socket wrench).

Step 2: Remove the belt

Loosen and slide the belt (it’s clearly visible) off the AC compressor.

You’ll need to loosen the nut you see on the outer side of its pulley for the belt to budge.

Step 3: Pull the wire connector off the compressor

The plastic wire connecting the compressor to the power supply is to be disconnected next (simply grab and pull it off the compressor).

Step 4: Remove the high (thin) as well as low (the larger) pressure lines

To do this, first remove the bolts connecting the two pressure lines to the AC compressor.

You then separate each from the valve on the compressor.

Now, before you proceed with the steps of adding oil to air compressor, you must capture the Freon.

You know the risk if you fail to do this: it might escape to the environment causing harm.

More importantly, it could put you in the crosshairs of the Environmental Protection Agency (EPA).

What you’ll need for AC refrigerant removal:

  • A reclaimer machine


Step 1: Connect the gauges of your reclaimer machine

When connecting, begin with the low side (the bigger tube) followed by the high side (the smaller line).

Step 2: Purge air from the hoses

Any air trapped in the hoses could bring problems down the road and you want to get rid of it.

Simply hold the yellow hose and point it away from you then open the low side for about one second followed by your unit’s high side again for 1 second.

This should clear the hoses.

Note: You must close the two sides after you’ve completed purging.

Step 3: Connect to your IN and OUT sides

Now connect the yellow hose to your reclaimer machine’s IN port and the extra yellow hose to the OUT port.

Step 4: Purge air from the machine

To remove air from the machine, release gas from your low side again for 1 second.

Step 5: Connect to the recovery tank

Now connect the remaining end of your yellow hose onto the recovery cylinder (to the liquid port).

Step 6: Open the gauges (the low side)

Next, you want to open your gauges’ low side.

Also (please check that both ports on the recovery machine are open before this) open the valve on the recovery tank.

Step 7: Recover the refrigerant

Turn on your machine and wait until the gauges have dropped to zero.


Close the valves and turn the recovery machine off.

Lastly, disconnect the two valves from the compressor.

How to add oil to air conditioning compressor – final steps

With the refrigerant out of the way, proceed to add your specific air conditioning compressor oil (check manufacturer’s recommendations).

Step 1: Pull the compressor out

Unscrew the other 4 bolts holding the compressor to the car and pull the component out.

Of course, you’ll have to disconnect everything else to be able to make it come out- lines, wires, and the belts.

Tip: The unit is pulled out from the top in some engines and via the bottom in others. Check your manual if unsure.

Step 2: Drain the old car AC compressor oil

Unscrew the compressor’s rear cap with your hands and allow all the old oil to flow out of the part and into a suitable container.

Shake it back and forth until all the fluid empties out.

Tip: You don’t want to mix oil and new oil because of the risk of overflowing. The unit may also develop operational problems after installation as a result.

Step 3: Add the correct quantity of oil

Verify from your owner’s manual or from the internet the amount of oil your compressor needs then pour this exact amount in there.

Simply insert a suitably-sized funnel into the opening then proceed to pour the fluid.

Finally, fit the rear cap back into place and screw it securely with wrench.

Tip: The last thing you want is to spill the oil so pour it slowly.


Step 4: Cycle the compressor

To have the lubricant circulate to every corner in the compressor, spin the clutch plate about 3-4 times.

Here is the correct way to cycle the compressor:

While holding the compressor in one hand, rotate your clutch plate 3 or 4 times.

Step 5: Reinstall the compressor

Fix the AC compressor back to its slot and mount the 4 bolts you had previously removed. Be sure to tighten then adequately with your wrench.

Step 6: Recharge the Freon

Proceed to charge the Freon back into the unit with your reclaimer machine.

Step 7: Restore everything else

To complete, hook the two pressure lines back to their positions. Be sure to re-mount their securing bolts (you need to tighten them as well).

Next, reconnect the wire connector and finish by re-sliding the AC compressor belt onto the pulleys and tightening the nut you had loosened earlier on.

You obviously need to return the plastic cover to where it was (plus its securing bolts).


How to add oil to air conditioning compressor – alternative method

·         Use of an AC compressor oil injector to refill the compressor.

Another way of adding oil to the compressor is by use of an oil injector.

Simply fill it to the required level and clip the injector’s valve to your compressor’s lower side pressure valve.

All that remains is to push in the oil slowly.

Note that you may need to refill it and pour the contents several times for the oil to come to the required level.

Keep in mind that the A/C may need to be running and the AC compressor on before pushing the contents in.


How to add oil to air conditioning compressor – Useful Tips

  • Your owner’s manual should help if you’re struggling to locate your AC compressor.
  • Always park the car on level ground before starting the operation. Also engage the parking brake.
  • The best way to tell if you’ve added oil the right way is to start the car engine and check if your air conditioning system is cooling perfectly.


Final words

Don’t try to add more oil than indicated in the manual, even if your compressor seems half empty – doing so will be asking for more trouble.

Something else: If this proves too much of a hassle, consider taking your car to a qualified mechanic.

You don’t want to take shortcuts and cause more issues in your AC compressor or other parts of the AC system.


Do new AC compressors come with oil? We answer

Too much oil in AC system symptoms and troubleshooting tips


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