The center of my AC clutch has fallen out of the pully. I can push it back in but it doesn't stay. What's missing? Also, my heat hasn't been working but I have (had) ice cold AC. I haven't used anything since it fell apart because I'm afraid to ruin anything more than it already is. I'd like it if this was a simple fix.

 

I had that happen before and I replaced the clutch. After doing so, I turned on the A/C and it instantly ruined the new clutch. Like yours, my A/C was working perfect before this happened. It turned out to be my compressor; it was completely locked up. Replaced everything except the condenser and has worked great ever since. Shop for parts on the Internet, do some reading, and do it yourself and you'll save a ton of money.