I just purchased a 79 300d for my son in law to drive. The ccu is totally non funtional. To get heat you have to open a valve under the hood, make sure the A/C compressor is unplugged, and flip a toggle switch (inside the car) to turn the blower on. If you want A/C you close the valve on the coolant line, plug in the compressor, flip the toggle switch for the blower, and another toggle switch for the aux fan. The main problem is the blower operates only one setting, high. Is there a way to wire the blower with a high and low setting? Also, anyone know of a cable activated valve that I could rig up for the heat control?
I'm not going to try to make this system perfect but its a PITA to have to open the hood to make adjustments for heat and A/C.

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a few mb diesels

your best bet would be to find out what parts have been removed or are inoperable and repair the system.im sure someone at this site will be familiar with the CC for this model.a 79 i beleive has the CC servo system and there is an updated replacement available.try a search on CC servo

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michael cole 1980 300SD gone now but not forgotten,87tdt,90 300te 4matic 95 e320 wagon