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.

I just realized that I was faked out, there are THREE hoses (even MORE confusing!) coming out of the firewall that seem to make a double circuit through the evil servo with this fourth tiny hose going back to the water pump. I'm theorizing the tiny hose is meant as a temperature differential signal to this valve on it that turns on the fan by vaccuum (of course!) when the water is hot enough ?

So I could possibly just pull the evil servo aside and put in two 3/4 in PEX type valves with a barb into each of the four hoses there?

Then just find some 12v positive wire under the dash, run a resistor thru a switch to run the fan at less than 13.2v at running ?

Does that sound like it would work for now ?

Thanks!

It's possible that the blower resister remains on your car. It is almost certainly located under the hood and not within the dash. However, I am not familiar with your car.

I used to have a 1980 300d and I did in fact bypass the servo one winter. Just turn on the valve during the winter and shut it off during the summer. Works great, but eventually I just bought a used servo.
Check it out...

Wow! This may be what I am looking for... I Just bought (proudly!) a slightly rusty bottomed 1982 300D. The heater has been bypassed, i'm told. I do have the haynes book, but am on a serious budget. I will do with love what some do with money. However, I need to know if the cool ball cock valve (the copper is OK?) there with all the (pex?) tubing will work in the '82.
I also don't mind giving it a turn twice a year, seasonally, but Where Would All The Tube Ends Go?

I am a -very capable- newbie, have changed timing belts on dual overhead gas camshafts, and now am ready for the diesel gorgeousity.
Help?
Thank you,

__________________
Guillermo
1982 300D Turbodiesel 117K, future WVO combustor
http://statework.blogspot.com
and
http://www.thestateworkers.com

Hey By the way, the car was out in a front yard in Butler NJ for at least a couple of seasons, and I think the water pump is toast (leaks coolant upon start up somewhat heavily, and overnight, slowly)
What should I replace at the same time, and what's the difficulty level of the undertaking?

-You know, I really like the room afforded hands and elbows in there. Not at all like the Mazda 626 crampymechanicmobile. I'm loving the Benz already.

__________________
Guillermo
1982 300D Turbodiesel 117K, future WVO combustor
http://statework.blogspot.com
and
http://www.thestateworkers.com

Click on the Resources tab above and look in the DIY Articles.
"Auto to manual climate control conversion on 1978 300CD" By "GAVIN LESLIE"

Or pull the entire manual heating out of a 240D and swap it in. as he said, it would be easier.

Charlie

__________________
there were three HP ratings on the OM616...

1) Not much power
2) Even less power
3) Not nearly enough power!! 240D w/auto

Anyone that thinks a 240D is slow drives too fast.

80 240D Naturally Exasperated, 4-Spd 388k DD 150mph spedo 3:58 Diff

We are advised to NOT judge ALL Muslims by the actions of a few lunatics, but we are encouraged to judge ALL gun owners by the actions of a few lunatics. Funny how that works

Hey thanks!

Good news- she seems to be getting happier:
the turn signals , which had a good fuse & bulbs but weren't working, resurrected themselves out of the blue, while doing 65 on route 80 last night! Such a relief not to use the parking lights when turning, I was afear'd that tracing the bad wire was going to be rough.

I've got another question (Big surprise, prob'ly not the last...)- Since changing the engine oil it starts and runs so much nicer, but it had horrible black balsamic vinegar colored stuff in there. I changed it, ran it for a day then changed oil & filter again and, ok, now the dipstick looks clean.
But the Oil Pressure gauge , which comes right up when I start it, reads constantly pegged or just shy of 3, and comes down to 1.5 bars or so only when the car is warm and idling at a light. Is that Ok?

What are the possible causes of That wierdness?

__________________
Guillermo
1982 300D Turbodiesel 117K, future WVO combustor
http://statework.blogspot.com
and
http://www.thestateworkers.com

Your oil will be just as black the next time that you drain it for a normal change, or earlier if you are just curious. Diesels generate soot and a lot of it ends up in the oil, that is why it is so important to use diesel rated oil and to change it on time.

As for the oil pressure, it should be pegged at all times when running, and drop back to 1.5 to 2.0 when up to temp and idling. The gage does not read full oil pressure when running, by design!?!

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1961 190Db retired
1968 220D/8 325,000
1983 300D 164,150