My mother-in-law has an 01 JGC with a strange starting problem. She says the thing won't start when the A/C is on. I thought this was a little odd and kind of blew it off. Well, this has been going on for a couple of weeks now. Last night I was over there and she mentioned it again. I decided to go out and get a look first hand. Sure enough, I tried starting it with the A/C on and it would crank fine, but not fire up. It turned off the A/C, tried it again and it fired right up. I turned the A/C on again and tried again - this time it started. So, this is intermittent. I tried starting it again with headlights etc on trying to put a load on the battery and it started fine. The battery and starter sound strong. Keep in mind that I only messed with the thing for a few minutes, but I have never seen anything like this before. Others on this forum have posted unusual starting problems and they reported that the battery terminals just needed cleaned. Though this doesn't line up with my past observations regarding dirty battery terminals, I will give it a try. Any other ideas?

i've seen some people had to have the PCM reprogrammed or the AC compressor clutch replaced when they experience problems related to the AC and engine running (or not running).