How to Replace a GMC A/C Compressor

by Eli Laurens

General Motors automobiles use a compressed freon air conditioning system that has a rotating compressor driven by the engine. This compressor requires internal lubricant that usually leaks out of the many joints and gaskets of the system; loss of this lubricant can damage the compressor bearings. An electrical clutch plate can also become damaged or wear out. The average backyard mechanic can replace a GMC compressor in about two hours.

Evacuate the air conditioning system by taking the vehicle to a Freon reclamation facility and having the Freon removed with professional equipment. Most garages and oil change centers will do this for free, as they get paid for collecting freon. It can also be recycled. Do not vent the Freon into the atmosphere.

Disconnect the battery by turning the positive terminal bolt counterclockwise.

Disconnect the freon lines from the compressor by turning the line bolts counterclockwise using the line wrench. Store them out of the way, but leave them connected to the other air conditioning equipment.

Remove the drive belt from the compressor's pulley wheel by pressing the tension pulley arm firmly and sliding the belt from the idle pulley. Once free from the idle pulley, the belt will have enough slack to remove it from the compressor pulley wheel.

Disconnect the compressor from the wiring harness by pulling the adapter plug from the top terminal on the compressor.

Remove the compressor mount bolts by turning them counterclockwise, then sliding them out of the mount arms.

Manipulate the compressor from the mount and out of the engine.

Replace the compressor by positioning it into the mount arms, and tightening the mount bolts in a clockwise direction.

Reconnect the wiring harness by pushing the adapter plug into the terminal on the top of the compressor.

Replace the drive belt over the compressor pulley wheel, then press the tension pulley arm firmly to slide the belt underneath the idle pulley. Release the tension pulley arm and the belt will tighten.

Reconnect the freon lines by turning the line bolts clockwise, checking the gaskets for damage and proper seating.

Reconnect the battery by turning the positive terminal bolt clockwise until it is snug.

Refill the Freon using the proper equipment and GMC guidelines. The typical GMC system will hold between 1 and 2 lbs. of Freon.

Tip

  • check Convert from R-12 to 134a when replacing the compressor, if applicable.

Warning

  • close Use extreme caution when working with Freon.

Items you will need

About the Author

Eli Laurens is a ninth-grade physics teacher as well as a computer programmer and writer. He studied electrical engineering and architecture at Southern Polytechnic University in Marietta, Ga., and now lives in Colorado.