86 535i Heater won't shut off!

Any help would be greatly appreciated. I can't get the heater to shut off. It continuously has hot air coming out of the defrost vents on the dash, I can't get it to stop; even if I turn on the a/c full blast and it's blowing out cold air, the hot air still is coming out the defrost vents. Any ideas?

Check to see if the plug on the heater valve itself is still connected. I would remove, clean and reconnect. If this doesn't resolve the issue your temperature controller is dead and needs to be replaced.