Climate control issues

[ncinirator]

Hi guys, long time no post.

I have an 89 9C1. The climate controls work, but not correctly.
If the climate control is all the way to the left in the cold range the air comes out cold. If you move the control to the right to mix the air and make it warm, after sliding the control a few centimeters from the cold position I can hear the vacuum hiss and the air comes out piping hot. There is no medium or warm, its either cold air or hot air.

I researched threads and no one seems to have had this problem. I don’t know anything about climate controls on cars, so I’m turning to the forum for help.

Help!