My Car Seems To Be Overheating When Ac Defrost Or Anything Like That Is On.

I recently had a new timing belt installed in my 2001 honda civic. My ac went out in it like two weeks before I had the timing belt replaced so I had my mechanic look at it while he was in there. I can exactly tell you what the problem was with my ac was, but maybe you expert mechanic can piece together what I’m about to type and make some sense out of it… My mechanic said something like there’s a clutch that has the ac belt on it or something and it got broke off. Anyways I was needing my car really bad and he couldn’t get the parts for it right away to fix my ac so he just put a new timing belt on it and let me have it. I didn’t have any problems out of my car until maybe a week later I was driving though some rain and my windshield fogged up so I cut on my defrost. Before I knew it my car was getting pretty warm so I would drive it until it got kinda hot and I’d cut my car off and coast so it wouldn’t overheat. I really didn’t have no idea what the problem could be until I realized my car only did this when I cut the defrost on. So I experimented and it also does it when I have on any kind of air whatsoever. When it does it, it so erratic an it might be several miles after I’ve had my defrost on and cut it off that it does it and it could go on a while after it’s been cut off. It’s just so aggravating and odd and I was just wondering if somebody might know possibly what the problem might be. I took the car back to my mechanic and he just seems pretty stumped about it. But anyways, that for any info y’all might have guys. I really appreciate it.

Thanks