I have checked the heater valve and there is no vacuum at it. Does anyone know where the vacuum control for the heat valve is located? I tried to trace the vacuum line , but it goes under the heater box and I could not find where it goes from there. I also checked the rheostat with an ohm meter and it seems ok. Does anyone know of any other possible fixes for this problem?

 

Blend door actuator or broken blend door. It's behind the glove box . Little white box.