I just started having a problem with my A/C on my 2001 XJ.

I noticed that it was blowing warm air and it turns out the a/c clutch wasn't engaging.

a couple hours later when I tried turning the a/c on again it worked.

What would be the causes of intermittent operation?

Low refrigerant?

Bad switch?

Any idea?

 

I would start with the relay over in the pdm first there usually only 9 or 10 bucks and usually an intermittent clutch problem is the relay good luck

 

Sounds like a low freon charge. Find someone with guages to see what the system is doing to verify the problem.

 

Mine was doing the same thing. I started the engine and started trying things like jumping the wire for the relay, nothing. I happened to pull the high pressured connector and plugged it back in and it started right up. Worked since then. I figured that there must have been some corrosion in the plug. Might not fix yours but something to check.

 

Low freon won't not work then a year later start working again. The way it works if it has low freon is it will cycle on and off as if it's in defrost mode. If this is what it is doing then stop using it as you will burn up the compressor. However I think it's either a switch or the clutch itself...

 

Question. Who said anything about a year later?
You are correct about a low freon charge which is what I mentioned. What you are describing is called short cycling. The best way to diagnose this is with guages. I also agree with checking the connections and the pressure switches as well.