climate control in 1998 blazer

1998 model with thermostatic climate control. Fan works properly, air direction works properly, all buttons on control head work properly, but the air temperature stays at max hot. Any ideas?

Blending door is stuck or has become inoperative or the temp dial is defective.

Switch from cold to hot and listen for the door moving.

it sounds like the acuator door is stuck or went out.mine would only give me cold air when it went out.

i can hear what sounds like a "door" or something moving back and forth while I'm sitting still. Thanks.

i can hear what sounds like a "door" or something moving back and forth while I'm sitting still. Thanks.

Huh?

1998 Blazer overheated and now won't start any suggestions where to begin