Heater control valve question

[firepop5]

96 V8 Explorer with automatic temperature control.

What position is the heater control valve in if the system is turned off?
Should the valve be open or closed when there is vacuum to the valve?

Heater operation seems erratic and I'm trying to tell if valve is bad or blend door is on the way out.

Thanks

 

[Chikar]

This is from a 98 with EATC. I'd expect your 96 to be the same.

When OFF is selected:
•The A/C inlet duct door is at full vacuum, closing off outside air and admitting only recirc air.
•The heater water control valve is at full vacuum, preventing hot coolant from reaching the heater core.
•The floor/panel and panel/defrost doors are at full vacuum, closing off the passages to the A/C registers.
•The blower motor and the A/C compressor are off.