Please help.

Okay i few months i unhooked up my hvac unit and pulled it out of my car since i was putting a 7.2" screen in dash and i had to fiberglass a whole new panel. Well after completing the screen, i go to hook the hvac back up, and it wont blow anymore. I have a 98 sunfire. So i get on ebay and i get a new hvac unit out of a 96 cavalier to try and swap to see if it works. Well i plug it in and it does blow cold air now which it didnt blow at all before. But the weird thing is, the hvac unit will only light up on a few settings and the others it dont. The defrogger light wont turn on when i push the button in but it works. So i was messing with it again today and found out the hvac unit fuse was broke, so i fixed that. But now my hvac will turn on without the keyes in my car at all, and the car not EVEN running. How could that be possible to have power when the keys arent even in the car. Would there be a chance that one of the fuses in the engine compartment under my hood is blown to like one of the black fuse boxes. Maybe one of those blocks are bad which is making my hvac unit have power all the time. I didnt know how to check those without really putting a new one in.

Before i unhooked this hvac, before any of this, my ac and hvac did work fine.

Please everyone post if you know what it could be.

thanks