Look for a broken vac line up beside the brake booster. There is a "y" connector there, one leg goes to the dash vac guage (which probably doesn't work, eh?) and one goes to the climate control. No vac, you don't have anything but defrost.

If there is nothing obvious, get a MitiVac hand pump and see if the system will hold vac (there is a tank in there, too, so it will take a while to pump down). If so, the connection to the manifold is bad, fix. If not, pull the glove box by prying out the little plastic center pieces on the rivets and then remove the latch at the top (two screws). Pull the center of the top edge down (there is a hook molded in it) and pull glovebox out. On the right side of the heater box is a switchover valve with about 8 vac lines on it. Top one is the supply, the others are lines to the various servos.

Pull the supply line and make sure you get vac, then pull the servo lines off one at a time and see if the servos work.

Chances are you have a bad supply line, but you will need to replace the servos if they leak. This is a BIG job (do a search for procedures).

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!