[islan]

The black line coming thru the firewall to the first vacuum block is the vacuum in. the grey thru the firewall is to the heater valve. Have to remove the glovebox and the computer housing (2screws usually) tho I only put the bottom screw back in. There is a soft ruber or plastic bulkhead conection thru the fire wall about the top front of the computer housing and you can wiggle it around and pull it into the cab. Good chance you have a break right on the engine side of the firewall and if so it is easy to run new lines all the way back to that silly little vacuum supply valve on the manifold and to the heater valve too.

Can't tell you how to reach,see or even guess about the diaphgram on the drivers side with puling the instrument cluster, and not sure about it then.

I have the same problem and got this far last year but this year floor and defrost only. I am going to tee into the vacuum line going to that diaphgram and use a manuel vacuum pump and see what happens. At least then I'll know if it is a leak or a bad actuator diaghpram.

Good luck and if you find a schematic or diagram for this let me know. I've looking for a year.