I have ~54k miles on my wagon, and moved this June from the relatively cool climate of Massachusetts to the desert of Arizona (high temp today
106F=41C). I never used the air conditioner much before I moved here.
Since I've been here, I found the A/C had the annoying trait of never working when the car is at idle or just above. I don't think it did this before, but I'm not certain. When I sat at stop signs or traffic lights in the congestion leaving school, I'd have to keep the engine rpm near 2000 for the A/C compressor to remain on. Otherwise, it blew hot engine compartment air at me. The A/C indicator light never went off. Under the hood I saw it A/C compressor was running for about 10 seconds and then turning off for a minute or so. I wondered if it was similar to the rapid cycling issue brought up on this NG before.
At speeds greater than 25mph, the system worked just fine (as in full blast recycled cold barely kept me from sweating in bright sun).
I did a battery test for a reason unrelated to the A/C, and found it was going dead even though it's less than three years old (and out of warranty). I wasn't yet having problems starting the car or running any other accessories. Apparently two years is an average life for a battery in greater Phoenix. I replaced mine today.
The A/C now stays on at idle. I can feel the compressor shut off occasionally, but it cycles back on again before the system tries to melt me.
I wasn't expecting a new battery to help, but it did. I guess the alternator can't provide enough amps until the engine turns faster, so the battery is asked to take up the slack. YMMV.
- Byron