I have 2 q's. first off i got an 1993 325i bmw. on the key there is a button but it seems as if it does nothing. is it supposed to? do i need to change the batteries and how? second Q is I have AC but barely any cold air comes out, it blows fine but just hot air, so what part of the AC system do i have to buy to fix this? thanks

I don't know about the key. The AC failure could be any of several components or sensors or it could be as simple as low refrigerant. You should probably have a good shop look at the AC.

Its usually just a watch battery that you can replace if you pry apart the mechanism with something like a chisel, key or knife. Just go easy so it doesn't break. Usually though, those things go to hell after a few years of the microchip getting banged around so a new battery may not accomplish anything

thanks