1985 300sd Air Condition Vent Question
 

All of the air is coming out of defrost. Is there a simple way to repair this or manually open to get air out of vents? Thanks in advance Jack:confused:

simple? ... dig into the dash and wire it open?
the 85 is fun to work on... you could try a ccu resolder...

Don't know how much different the 85 is from my 83 but a thing or two I found while trying to diag that same situation with minelast year. The diaphragm above & to the right of the accelerator works the flap that sends air to the vents. During my testing with a hand held vacuum pump on that diaphragm, I was able to keep it open by pulling vacuum and plugging the line to hold the vacuum. My problem ultimately turned out to be electrical - the switch-over valves on the right side of the console.

Look at the switchover valves just to the right of the radio.
You may be able to manually steer the air by re-routing vacuum from there.

Get a "Mighty vac" and check the valves, pods for leaks and fix it properly.

I just had to repair this same issue on my 85 SD. Turned out to be two bad switchover valves. One had an open coil, one leaked. Easy fix when you understand the system.