My 94 vette climate control will not let me increase the temp setting, but I can decrease it. In the morning when the car has set overnight the up temp contron works, but after the car has been running it won't work. Any Thoughts?...Bill

 

Look for "89 HVAC problem" posted on 10/9/05 in this forum. Someone else had a similar problem (as I did on my 94) as you are experiencing. I posted an explanation of how I solved it on mine. I guess it didn't work for him but it's free to try before you start replacing things and just takes a little time and if it works it's pretty rewarding.