Rick's Free Auto Repair Advice

Replace an Auto AC Compressor

How to replace an auto ac compressor

If the AC compressor has failed on your vehicle and you want to replace it yourself, here are some tips from the pros. You can replace an auto AC compressor yourself as long as you make sure you’ve added the correct amount of oil. There’s oil inside the compressor crankcase and oil throughout the AC system.

The oil in the compressor crankcase lubricates the metal moving parts, while the oil in the system is carried by the refrigerant to lubricate the compressor’s pistons and valves.

Step 1 Evacuate any remaining refrigerant and measure how much oil came out with it.

It’s illegal to vent refrigerant into the atmosphere, so you should pay a shop to evacuate, recover, and measure how much oil came out. It’s important to recover the refrigerant for environmental reasons, but it’s even more important to recover it to find out how much oil came out of the system. Because you’ll have to add that same amount back into the system before you refill it.

Skip this step and you risk under/overfilling the system with oil. If you underfill, you’ll cause premature compressor piston/seal and valve failure. If you overfill, you’ll dramatically reduce cooling.

Step 2 Remove the old compressor, drain and measure

Remove the AC compressor drive belt. Then disconnect the AC lines from the compressor. Remove the retaining bolts and remove the compressor from the vehicle. Be careful not to spill any oil as you remove the compressor.

Remove the compressor crankcase drain plug and pour the oil into a measuring cup. Tilt the compressor to drain any oil from the suction and discharge ports. Wait a few minutes for the remaining oil to drain down, then rotate the compressor shaft one-half turn every minute, for up to three minutes as you continue to drain and measure. Tilt the compressor back and forth several times while doing this to drain out as much oil as possible.

Step 3 Drain the oil from the new compressor

Remove the compressor drain plug. Using a fresh measuring drain auto ac compressordevice, drain the oil from the new compressor following the steps above. Then add as much new oil back into the compressor as you took out of the old compressor. Reinstall the compressor drain plug.

Step 4 Flush the system and add oil

If the compressor suffered a catastrophic failure, you’ll have

AC system flushing kit

Flush with an AC compatible fluid and flush it.

to replace the receiver/drier and condenser (check this post to see what types of condensers can’t be flushed). However, if you have a condenser that can be flushed, flush it with a special AC flushing kit. Then flush the lines and evaporator.

If you replace the condenser and receiver/drier, add 2-oz of oil in addition to the amount of oil that was removed during the initial evacuation.

Step 5 Install the new compressor

Rebolt the compressor to the engine and mount the AC lines using new gaskets/O-rings. Reconnect the clutch and any other electrical connections.

Step 6 Evacuate and refill

Evacuate the air from the system and then recharge using an AC refrigerant scale. See this chart for the proper amount of refrigerant.

©, 2020 Rick Muscoplat

Posted on by Rick Muscoplat

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