Tallguy67

Ok, so if try to interpret what is being said in the brief posts above, once the engine is up to temperature if you turn the **** on the dash you either get very hot air or cold air out of the vents.
If my assessment of your symptoms is correct then you do not have a thermostat problem and you do not have a vacuum problem. Thermostat problem would affect the temperature of your coolant and the coolant wouldn't get up to temperature.
Vacuum does not run the door that mixes hot and cold air. Vacuum operates the door that chooses whether air goes to defrost, dash vents of floor vents.
The door that adjusts the mixture of hot and cold air is called the blend door I believe and it is operated by a motor. There are lots of blend door problems diagnosed and repaired on this forum, search on Blend Door.

Hope that helps.

Busboy

Check your coolant level I believe it's low or has an air lock.

KATOOM

What temperature dial? The engine temp gauge or the hot/cold selection **** on the HVAC system? I think this is confusing some of us.....