New Battery Disappeared/Air Conditioner Which Worked Fine, Now Doesn't Work

Earlier this year, I bought a brand new battery for my PT Cruiser. Well, I am trying to sell the PT Cruiser, but not having any luck with the dealer I left it with, so I went and got it. The battery that is on there now is corroded --so obviously it is not new. Also, the air conditioner doesn't work. It was working fine when I left it.