1989 760 Turbo AC and heat - no air from vents

The AC and heater work fine, and the fan is blowing. However, almost
no air is coming out any of the vents. Anyone have a diagram of the
probable bottleneck?

 

First the obvious, are the vent dampers open? They're the oreo cookie
things, some people don't realize what they do.

If that's ok, I'd start looking for a vacuum leak, the main dampers are
vacuum operated and they close with no vac.

 

Many thanks. Your solution sounds logical. I'll try to have a vacuum
leak found. Also, where are the main dampers?

 

They're burried behind the dash in various places. They're vacuum servos,
like miniature versions of the cruise control servo under the hood. Usually
the problem is the vacuum resivoir behind the bumper, you can ask Jamie
about that, he knows all about it.

The early 760s had a climate control that was entirely vacuum operated and a
nightmare to work on. I think yours has the later electronic version which
is not as bad, still wouldn't hurt to check all the fuses though, IIRC
there's a bunch of solenoid valves that control vacuum routing.

 

Wish I had 1% of your mechanical acumen! Thanks for the counsel.
I'll get on it.
George