Intermittent A/C ???

Hey guys! Me again with an A/C question. I have a '99 Cherokee Sport 4wd, 4.0 with 157K miles. Recently the a/c has become intermittent. I think the alternator is going bad as I asked about in my post here. My wife has come home several times now saying the air is blowing out hot. When I start the car it blows cold enough to fog the windows. When I drive it the air is cold. The compressor is cycling off and on. I bought the Jeep new in 99 and since owning it pretty much the entire A/C system has been replaced. It's been the only real repair work it has needed. The compressor seized and it and most of the under hood components were replaced about 4 years ago. About a year to year and a half ago the coil in the dash was replaced too. Any thoughts? Related to the alternator? I'm not very versed with A/C. Any help you can give will be very appreciated!

-BDHershey

I think you'll need to isolate the two problems first. The very first thing I'd look at is belt tension, to make sure both problems aren't just related to a slipping serpentine belt. Do not depend on squealing to tell you if the belt isn't tight enough. It doesn't always make noise, even if it slips.

Once you've got the tension, then you need to see if the alternator really is going bad. If it is, and if the voltage drop you're observing in the other thread is still occurring, I'd guess it's possible that it's enough to disengage the compressor clutch. Anyway, if you need a new alternator, you'd better do that first.

However, if the compressor is cycling on and off without being messed up by low voltage, that usually means low refrigerant.

My 99 has had that problem, as well as occasional icing, which has a similar effect, except you don't hear the compressor cycling. I also had a problem last year with the compressor clutch sticking owing to rust. It would engage for a while, then start slipping after a few minutes. That's not a hard one to diagnose, because the clutch gets really hot when it slips! A big dose of penetrant and a few whacks upside the head got its attention, and it's worked all year since.