Well, Ive had that problem w/ the first car I owned ( 2002 Cavalier ) and I am currently having this problem w/ my PT Cruiser. My 2006 PT is starting to blow warm and slightly cool so I think it's time for a Recharge ( seems kinda early to me at only 2yrs and some change old w/ 47k, but I suppose it happens ) When I am driving w/ the AC on the car is fine, but when I am at a red light or parked for a short time the fan is on, the car isnt over heating or anything but I can hear the compressor going on and off and it really jerks my car, like I can feel it shutter hard. For a 4cyl it does take power from the motor ( so they told me when I had the same problem w/ the Cavalier, is that info true, not sure but at the time it made sense ) Does your AC Blow warm when stopped or parked, then cool off as you drive? Maybe I'd suggest get it checked for a recharge, hopefully that'll be it. I hope there's no crack in a pipe or AC compressor, but I'm sure that's not the case.
