Bernard is great, we've bought about half a W115 from him, one or two bits at a time.
Several things to check:
1: If you dont' have vac to the climate control, the only thing that will work is the temp control (ie heat from the heater core and AC compressor on or off) because the master relay requires a vac signal to switch the fan on. Master relay is behind the glove box.
2: If the blower motor is shot, you won't get anything but road draft air flow out of anything. However, if you have vac, the the flow should be coming out the dash vents on AC mode and up the windsheild on defrost.
Here's what I would do: toddle on down to the autoparts store and get a MitiVac hand pump (you're going to need it to fix the door locks soon anyway), open the hood, disconnect the green plastic vac line up by the brake booster, attach the Mitivac and pull a vacuum. There is a vac tank, so it may take some pumping.
If the climate control runs properly with vac applied thusly, you have a vac supply problem. If the line is busted or loose, that may be all that is wrong.
If the lines are OK, hook the Mitivac up the engine side of the green line with the engine running and see what you have for vac -- should be 17" or so. If not, check for breaks, bad rubber connectors, or a plugged orifice (looks like a while or yellow plastic butt connector).
If you have vac, and you don't hear the vac servos moving the flaps as you change modes on the PBCU, check the top and bottom of the fuse in the fuse box to make sure you have juice to the CC.
If everything works but the fan, you need to unplug the connector under the passenger side dash and apply power directly to the blower motor. Must spin -- if not, bad motor or open resistor network so no juice gets to it.
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!