Today, on my second drive of the day using the air conditioning, the clutch started sporadically disengaging. The air would go from cold to lukewarm and humid, and the drain on engine power would be gone. Then, it would intermittently re-engage, and act as normal. Right now, with my car in the garage, if I turn the air conditioning on, I can see the compressor engage, and it stays engaged, blowing cold air. Any ideas what was causing this?

Prior to either compressor clutch or clutch coil failure, does either work intermittently or is it a sudden failure?

 

You are probably low on freon, or the pressure sensor is failing..

 

I added a little bit of R134a three days ago. The A/C now gets cold instead of cool, but this intermittent clutch engagement is new today.

 

If you're sure there is enough juice, the next thing I would look at is sensors. Something is telling it when to cycle. When the AC clutch is going bad, it usually quits working altogether. I have seen a clutch go bad and slip, thought somewhat rare.