How to Install an AC Bypass Pulley

by Robert Moore
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An AC bypass pulley is a free spinning pulley used to replace the AC compressor on an automotive engine. When the AC compressor goes bad in a vehicle, a consumer often will choose to install an AC bypass pulley. AC bypass pulleys are much cheaper than a new AC compressor. However, once installed the vehicle will no longer have air conditioning.

Step 1

Take the vehicle that is to have the AC bypass pulley installed to a local shop to have any remaining freon removed from the system.

Step 2

Lift the vehicle's hood and support it with the with the factory installed prop rod. Sketch out the approximate location of each pulley and how the belt wraps around those pulleys with the pen and paper.

Step 3

Attach the belt tensioner tool into the corresponding fitting on the belt tensioner. Release the tension on the belt by rotating the belt tensioner tool. While keeping tension off the belt, carefully remove it from around each pulley and set it aside. Allow the tensioner to rest in its natural position and remove the belt tensioner tool.

Step 4

Locate the two lines that connect into the AC compressor and remove them with the line wrench set. Follow the lines back to their other connecting point and remove them with the line wrench set.

Step 5

Locate the mounting bolts for the AC compressor and loosen them with the socket and ratchet set. Support the AC compressor with one hand and remove the mounting bolts by hand. Set the old AC compressor aside.

Step 6

Line up the AC bypass pulley mounting holes with the mounting holes on the engine that were originally used for the AC compressor. Begin installing the mounting bolts by hand and tighten them down with the socket and ratchet set.

Step 7

Visually inspect the serpentine belt for cracks or wear, and replace as necessary. Carefully route the belt around the pulley system using the sketched routing diagram. The belt should rest loosely around all pulleys except the tensioner pulley.

Step 8

Attach the belt tensioner tool to the belt tensioner. Rotate the belt tensioner by applying pressure to the belt tensioner tool. Slide the serpentine belt under the belt tensioner. Slowly release pressure on the tensioner tool until the belt tensioner sits on the belt and draws the belt tight around the pulley system. Remove the belt tensioner tool from the belt tensioner.

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