Rats; just wrote you a reply, and accidentally killed it. I'll try again.

If the recirc is not working, it is either the vacuum elements/servos that open the door, or the vacuum switching valve that routes vacuum to the servos, or the the climate control/recirc switch.

Odds are pretty good it's just bad vacuum servos; they get a hole in the rubber diaphragm and won't hold vacuum.

Look in the back of the glovebox liner and see if there is a small pop-out panel. behind this panel are the two recirc servos - see if they are moving the door as commanded. If not, then you will need to remove the glove box liner (pop-pins) to get to the servos; attach a small line and suck to see if they will hold vacuum.

Then, see if the vacuum lines are supplying vacuum as need to open/close the servos.
The vacuum supply to the servos comes through the vacuum switching valve, located behind the center console-right side. Pop off the long panel running down the right side of the center floor consol, and look up there to the right of the ashtray/radio area. the valve has 8 vacuum lines running to it that control all the servos. You can check the line color codes to trace down the proper vacuum lines. When the recirc switch is pushed, the vacuum switching valve will fire an electrical solenoid to the proper vacuum line, and allow it to suck. It's actually a pretty complex mechanical arrangement of the two servos, working thru linkages, and sometimes giving partial opening/closing; but you should be able to discern if one is not working peoperly.

This should get you going. vacuum elements can be bought here on fastlane, under "body mechanical and trim". The vacuum switching valve can also be bought here; but they are pretty expensive; I found a used on on ebay.
most of my vacuum elements have been replaced over th years, and I'm on my 3rd vacuum switching valve, one of those is probably the culprit.

DG