82 Heater problem

My 82 town car has a heater problem. It only blows luke warm air. I checked to make sure hot water was circulating thru heater core and it's doing fine. I'm down to the inside where the vacuum control behind the glove box is. It acts like it's drawing too much vacuum when I switch to hot because the blend door doesn't close (or open) all the way. When I unplug the vacuum line, the blend door closes (or opens) and I have hot air. Also, I checked the small vacuum switch just below the dash pad, and it doesn't act like it's bleeding enough air off, when I move the thermostat to the hot position. I believe it might not be working correctly. Any help would be greatly appreciated.

Hi JD...
I can't answer your Q:'s but I do have a suggestion for you folks with older Lincolns...

Try These folks too. (http://www.thelincolnforum.net/phpbb/viewforum.php?f=2) The oldies are all over there.