Another 1998 Heater Problem

OK, here we go. I have not hot air, only cold air blowing out of anywhere. I thought my Hearter Control valve was bad so I changed it. They I find out I have no vacuum going to the control valve when I call for Heat. I also find that I have very little, not enough even to open the recir door behind the Glove Box, when you turn the AC on Max Air. So it seems to be a vacuum problem, What should I do.