I bought a 1980 300D (nonturbo) that had been sinking into a field for 6 years ... it had been a parts car and the owner had removed most of the dash for heat controls.

It still has a working blower motor, i f I run electricity to it directly. But there's no water flow into the heater core.

Car runs great (well, OK, one of the cylinders is not fully participating by the lubbing sound and shake, but I get 25mpg, so I guess its not TOO bad.)

Pretty amazing considering that a shot of eather and a big jump and I drove it out of where it was literally sinking into a yard with a 6 year old inspection sticker!

So, the manuals I have (Chilton and Haynes) and the pdf manual don't give me enough detail to bypass the "evil servo" I keep hearing about. The dash has nothing resembling a "fan on and speed" 'switch, nor does the terrible wiring diagram or NONEXISTENT plumbing diagram tell me :

1) What is the max voltage to safely power the dash fan w ith? Its obvious from the smell and speed that its not supposed to get full 13.2v ! Once I know the max voltage, I can just rig a switch with resistors.

2) What direction does the water flow through the heater core?
Why are there FOUR hoses going through the firewall? Did this car have a driver vs passenger side heater core? There's nothing indicating any separate controls were ever there for that.

3) If I just take out the dead servo and this other thing that looks like a mini water pump and another thing that appears to be a voltage varied valve (monovalve?) and just put in a regular manual valve and a hose, can I manually turn on the flow into the heater core until I can figure out (replace and replace all the zillion vacuum hoses) the controls ?

DOes anyone have a detailed discussion and diagram as to hhow the "evil servo" works? What voltages cause which vacuum hoses to gain or lose vacuum and which switches on the dash do what at that detail level?

How the hell is the fan turned on and off ?

None of the manuals give enough detail ...

And at this point if I have to open the hood to turn a water valve to get defrost, that's OK with me.
But wich of the FOUR hoses would go where if I just bypass ?

THANKS!

PS: And I apologize if someone has already started a thread on this. I searched for about two hours two weeks ago and didn't find this discussion, if it was already started.