Heater Valve "Senior Moment"

I can't recall and searching didn't answer.

1988 w/4.0. Is the heater valve normally open (no vacuum applied) or closed?

I don't get vacuum at the heater valve on any setting. Can't suck or blow through the line either regardless of setting. HVAC doors all work fine. So does CC so no apparent vac leaks. AC works fine too. Heat comes on too when full hot so I suspect the valve is normally open. But then maybe the valve is shot and simply stuck open.

I'm pretty sure the vacuum engages on the cold side of the slider, meaning normally open. I no longer have mine though, so a simple way to know for sure is pop the vacuum line off the valve and see which end of the climate control produces vacuum and what happens to the flow.

No vac is open