2001 Blazer : I can not get any heat no matter where I set the dial. Thermostate has been changed. is the rotory dial mechanical or electric. [:-]

 

Have you tried flushing the heater core? If not I would try that.

 

flush flush flush...xInfinity...does wonders

 

I just had the same problem with my blazer. I flushed, changed thermostats and was even fixing to swap out the heater panel. Something told me to check all individual fuses. I checked each one and sure enough I had a fuse blowed that didnt even say heater on it but it shared the same circuit. I replaced the fuse and ever since, you can fry chicken in that bad boy. It will be the fuse box to the left side of your dash. Hope it helps.

 

Yes you probably need to back-flush the heater core. If you don't know what that means do a search on this forum, I'm sure you'll find it. And to answer your question the Temp valve (door as most people call it) is electric, just the temperature tough, the rest are vacuum controlled.