O.K. thanx ;

I'm not aware the Klima II was used in W-123's .

I guess the next thing to do is to dig out my multi - meter and begin testing and teach my self how this works , I'm guessing the MAX positions of the temp wheel are open circuit @ MAX heat and zero resistance @ MAX cold , I'll find out ere long .

Right now I'm on Holiday out of State , this means : very few tools and good finds in the local Pick-A-Part Junk Yards my Brother and I have been perusing ~ even a OM603 engine with cylinder head I failed to look at the casting # of . dirt cheap too , one of the few remaining Self Service Yards not bought up by LKQ jerkhoffs .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

I was going by your thread title which says Klima II. AFAIK, the W123 FSM does not have a useful wiring diagram for climate control system (only has power and grounds) so I can't tell you for sure how it is wired. I am pretty sure the temperature controller (multi pin silver box) receives inputs from the temp dial and varies the duty cycle of the monovalve to control heat output.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Thank you Kind Sir ! .

I am taking notes and will dig out my Multimeter when I get home again and begin testing .

FWIW : the often gone bad Monovalve part is here cheaply : http://www.***************/search/product.aspx?sid=2mrnah45sxaxmx45m5ev4sym&makeid=800016@Mercedes&modelid=1193576@300CDT&year=1984&cid=hvac@hvac&gid=12607@HVAC%20Mono%20Valve%20Repair%20Kit

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

I've read that cheap monovalves may have issues with weak springs and may latch from hydraulic pressure (coolant flow pressure) and not provide heat once it latches shut. I have not experienced that myself but it is something you should be aware of since there are quite a few reported cases.

Here's an easy test to perform to check your temperature controller (much better than a multimeter)

This video https://www.youtube.com/watch?v=IgqZ7icM1Io shows the hook up of a 12 V incandescent test bulb. One side of bulb goes to battery + terminal, other side goes to the brown/white wire of the monovalve connector (take the cover off). This essentially connects the bulb across the monovalve's coil since the black/red wire is hot with key on. Make your connections with key off since shorting the 2 wires will blow your push button unit. Connecting bulb to battery + terminal is less likely to short (and blow pbu) than connecting to the black/red wire of the connector.

This video https://www.youtube.com/watch?v=W-zuQZQB0ik was made with engine fully hot. As I turned the temp wheel further to the hotter position, then finally to the full hot (switch detent, can you hear it click?), the bulb's off time vs. on time increases till bulb is completely off. This is my 85 300D with ACC III (I believe that's what I have) and AFAIK my climate control system is working as it should.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

NAPA has Zerex. Sometimes it is available by the case for cheap. Ask NAPA for a discount or shop online if you have time.

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.

For these comments ~ My next step was to use a light to test the current at the Monovalve plug , I'm well aware that most of the time using a test light beats using a Multimeter but most don't have the practical experience and get lost arguing things they don't understand .

I'm back home now , the 31 year old Wagon skimmed across the Mojave Desert effortlessly as an old Mercedes Diesel usually does , even fully loaded with 6 passengers and luggage .

25 MPG going , 26.3 MPG coming back .

I am eager to begin this next round of testing and will report back what I find , might take a few days as I'm not retired yet and have the Foster boys etc....

I know I'd get detailed how to help here ! .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better