A/C short cycling... but only sometimes?

Maybe one of you can explain this to me...

I lent my '99 Cherokee to a friend to drive while her vehicle was in the shop. She ended up buying another vehicle, but that's another story... anyway, when I got it back I immediately noticed that the A/C seemed to be short cycling; that is, I would hear the engine fan spin up, then it would stay on for maybe 1-2 seconds, then shut off, then stay off for 3 seconds or so, then repeat.

I took it into my mechanic who's always been good to me and he said he could not replicate the problem. When I picked it up - he was right! it seemed to be acting normally. Then maybe a week or so ago I had reason to drive it to work and had to turn the defrost on because it was cool out and the windows were fogging up. Same short cycling behavior again. But later in the day it seemed to be operating normally. Any ideas why this could be?

I did have the A/C recharged a few months ago but haven't had any other problems with it. I believe that to be the first time the A/C has been serviced in years... I bought this from my cousin almost a year ago and I'm pretty sure she never had to have it serviced the whole time she had it.

thanks for any advice!

Compressor cycling up to ten times per minute (every six seconds) is considered normal, any more than that can mean your refrigerant is low. I'd have the pressure checked with a set of manifold gauges. If your low/high pressure is OK, then I'd consider replacing the low pressure cycling switch with a dealer part. There was a TSB issued in '99 regarding the replacement of the switch.

Number: 24-13-99
Group: Heating & A/C
Date: July 2, 1999
SUBJECT:
A/C Evaporator Freeze Up OVERVIEW:
This bulletin involves installing a revised low pressure cycling switch. MODELS:
1997 - 1999 (TJ) Wrangler
1997 - 1999 (XJ) Cherokee