When I got my blazer it all worked, but during winter it randomly stopped. No that it's not freezing I can be outside to fix it. no matter where I turn the **** it stays the same temperature. Also , if it is off air blows on my feet. I believe it's the blend door actuator but o need someone to back that up. Oh yeah, 1999 2 door blazer with 4wd. Manual climate stuff

 

That sounds like the blend door to me, it seems like its stuck. There is a thread on here on how to access it by going through the glove box. Remove the glove box and you will see it, supposedly it can be replaced in 30 minutes or so. Before you replace, you can remove it and check if it moves and if the little plastic gear is broken or not.

 

OK, I'll search around for it. thanks!!