1989 740 turbo wagon (360K)
Lost air volume to passengers compartment in all control settings.
The fan is working. You can hear the speed change for all 4 steps of fan control.
Air volume from vents very low and does not change as you slide the control slider from position to position.
where is vacuum takeoff from engine to operate vacuum controlled vanes in heater box?
Any other suggestions before i rip console apart??
Thanks

 

I found the problem. The line from the vacuum source in the engine compartment had come loose. The source line goes into the passenger compartment very near the exact center of the firewall. On my car the vacuum source line is protected, and can be identified by, a protective plastic shielding.