There is a temperature controller and fan speed controller behind the glovebox.
I put an '83 engine/tranny in my '85 car and after that the compressor would not come on. There are a couple pins that you can "jump" at the Klima to make the system work. I have been advised by a very knowledgeable forum member against running this "jumper" permanently because I may mess up the pushbutton unit. I have a good, spare pushbutton unit so I'm not too worried about messing up the one I am currently running. I will post which pins I jumpered later but you will be doing it at your own risk. I did it a few months ago and have not had any problems since.