You have either a leaking pushbuton control unit or a leaking servo, badly enough that all vac is lost when it is on. It could be as simple as a hose pulled off under the dash, but you will need to get a Mitivac and start checking.

I would also check for adequate vac at the main line -- it is possible for the restrictions (white or yellow "connectors" that have small holes in them) to get plugged, so you don't have enough vac to run things.

Check your check valves, the little round things in the lines, too, they can go bad and leak vac down. The locks should work fine a couple times even if the Climate Control bleeds off all the vac since there is a tank to store some under the left fender.

I suspect you have lots of leaking connections -- the little rubber bits between the plastic lines get hard (or mushy) and leak. Check them before getting too excited.

Locks are operated off the yellow line in the engine compartment, climate controll of the green and the vac from the cutoff goes to the switch on a brown line, to the cutoff on a brown with blue stripe.

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!