01 Heater Controlls only work on HIGH

[DaveM98Blazer]

Ive got an 2001 Chevy Cavalier and I hope someome here can help me out, I purchased this car brand new in 2001 and shes now got 35'450 Miles on her, shes been awsome without any majour issues, the only problems I have are the Heater/ AC Controll Knob only works on HIGH setting.

I was just wondering if anyone else has come across this problem and what was the fix?

I know in my 98 Blazer when this happened I had to replace the entire head unit and it was $$$$. For an 2001 Cavalier is it probably the same issue or is there possibly and relay or fuse issue?

also some of the radio controll button lights are out are these replaceable?

not so worried about the lights, BUT id like to get the heater controll thing fixed so it works on all levels as its terribel driveing around with the Heater or AC on FULL blast all the time as this is the only controll that works

thanks

take care
DaveM