How to replace the AC compressor on a GMC 1500, 2500 or 3500
Replacing the AC compressor on a GM 350 engine is not nearly as hard as it looks. The compressor is held to the engine by an aluminum cradle. The cradle does not have to be removed to replace the compressor. There are simply three bolts that hold the compressor to the cradle that have to be removed.
Note that this procedure only covers the physical swap of the compressor, not he associated tasks related to servicing the AC system after a compressor failure.
Begin by removing the freon from the system. If you want to have it reclaimed, take it to a shop that does this.
Remove the two electrical connections to the compressor.
Next remove the freon lines form the back of the compressor. The manifold is held in place by a single bolt. Mine was 15 MM.
Use a pry bar to move the belt tensioner and slide the belt off. I found the easiest pulley to get the belt off of was the smooth idler below the compressor.
With the freon lines out of the way, the bolts are much easier to access. There are nuts on the back and the bolt heads are held in place by a boss on the front. Mine were 9/16”.
With the nuts removed the bolts can be pushed out the front. However, it appears that they will not clear the clutch. However, there is a flat cut on each bolt. Rotate the flat to be next to the clutch and the bolts will slide out. A pry bar can be used to get just a little extra clearance if the bolt does not slide past easily.
On mine, one bolt also interfered with the fan shroud. I found that by removing the bolts that hold the shroud to the front header, the shroud could be moved enough to get the bolt out.
With the bolts all out, the compressor simply lifts out of the cradle.
With the compressor out, I had to swap a pressure switch that did not come with my replacement compressor. This switch is held in place with a snap ring.
Before attempting to slide the new compressor back into the cradle, take time to tap the bolt hole inserts all the way to the back of the cradle. This will make inserting the new compressor much easier. They will press back into the proper place when the nuts are tightened.
Slide the bolts back in by again aligning the flat spot on each bolt with the clutch and slide it in. Place the nuts on each bolt and tighten.
Reconnect the electrical connections to the compressor.
Secure the fan shroud.
Make sure the belt is routed correctly and use a pry bar to move the tensioner and slip the belt back in place.
Add the proper amount of oil and reattach the freon lines to the compressor.
You can now have the system serviced and the freon replaced.
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