I have a 1983 buick park avenue and I cant get
my heat to work at all. my heater blend door
works and the heater core gets hot there is no heater valve and has
good flows so I am confused. . and my vacuum
doors only open in ac mode should they work in
heater settings also

 

I assume this is not an auto temp control system...
Sounds like the vent directional door is not opening on heat (it should). The one that selects panel, defrost or heater.
Check the vacuum line coming from the engine bay for breaks or cracks, but if the AC part is working, then it is prolly okay.

This could easily be the mode vacuum switch on the control panel. Can you 'jiggle the (mode) handle" and get it to work? The mode switches should be available at Rockauto...

 

There is a vacuum control on the heater case, which is accessable after you remove the glove box-straight above the passenger's left foot- I think this is the control that I changed when I was having heating problems...round black diaphragm with metal links and a small vacuum hose...try that...

 

You can pull the little hose off, connect with a section of clean hose, suck on it, and see if it moves and does not lose vacuum.

 

the switch that controls the vacuum was bad and the parts store sold me a universal style heater core that wasn't functioning enough fixed those and I'm ok now first time having heat in 3 years in this car thanks

 

So the cold weather will be over soon and you will be complaining about the heat...