How to Replace an AC Compressor

car air vent

First, what does an AC compressor do? It's probably the most important part of your air conditioning system, ensuring the flow of refrigerant. So if yours is starting to fail, you'll notice the signs—the most common one being air conditioning that doesn't blow very cold anymore. You also might hear a lot of noise, such as chattering bearings or a squealing belt (if the compressor is seized up). The compressor's clutch also may not engage and will just stay cycled off all the time. While this may seem like a death sentence—especially in the height of summer—replacing AC compressors isn't the most complicated task. We break it down for you here.

Remember to wear safety glasses and latex gloves before you get started!

Vehicle System
HVAC
Skill Level
Intermediate

This is a project that needs some know-how

Time to Complete
3-5 hours
  1. Locate the AC compressor and remove the serpentine belt from the compressor's pulley. You may need a serpentine belt tool to work the tensioner and relieve pressure on the belt so you can take it off.

  2. You'll need to evacuate the system's refrigerant using a recovery machine. Recovery machines are specialized equipment that are limited to AC shops—you may need to take your vehicle in for this step before going any further.

  3. Remove the negative battery cable from its post.

  4. Remove the bolt at the compressor that secures the refrigerant lines and inspect the lines carefully for dirt or signs of wear.

  5. Disconnect the compressor's electrical connections.

  6. Remove the compressor's mounting bolts and pull the unit from the vehicle.

  7. Install the new compressor in reverse order. The warranty may also require you to change the orifice tube and receiver/dryer.

  8. Install and tighten the compressor-mounting bolts and hook up the electrical connectors.

  9. Replace the refrigerant tubes' O-rings and lubricate with the proper oil.

  10. Reinstall the refrigerant lines and put the belt back on the pulley.

  11. Pull a vacuum through the system to eliminate any residual atmospheric air or moisture. You'll need a vacuum pump and manifold gauges for this. There will be hoses that connect to the low side and high side of the system—these two connectors are different sizes, so there's no way to get it wrong. The gauges' yellow hose will then connect to the vacuum pump itself. Make sure all connections are completely airtight.

  12. Open the valve at the low side gauge while the pump is running—you will hear a change in the pump motor's tone as it starts to pull vacuum. Let the pump run for about 30 minutes and close the valve; it should read about 28 to 29 inches of mercury. Anything less than that can indicate a serious leak in the system.

  13. To charge the system once vacuum is achieved, reconnect the battery and connect the yellow hose to the refrigerant keg or can. Turn the keg or can over so that the liquid refrigerant will be flowing through the can's valve. Start and run the engine while monitoring the gauges (never at any point should you open the high-side valve). Put a thermometer in the interior AC vent while running the system on max setting and high blower speed. When the system is cooling at 30 to 36 degrees, your AC is charged.

Last updated July 3, 2017

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