Hello. This is an older thread, but I'm sure this happens more and more now that the cars are getting older. I had been having a similar problem, and I fixed my intermittent AC clutch problem by using a little oil on the clutch. I recharged the AC and had the same result, the clutch did not engage.

The AC was coming on when driving on the highway, but not engaging when city driving or idle.

I almost bought a new compressor today, and made an appointment to have it looked at (I get to cancel that now!) when I decided to put a drop of oil on it. It started right up, so of course I put MORE...and no I didn't get it on the belt.

So if you're having an intermittent problem like this, try a little WD40 or a garage door oil.

So we'll see how long this lasts, but for now it worked. I will update if it remains functioning or if it changes.