After much time and some parts replacement i have an airtight vacuum system in my 1982 300D turbo. The lock system works fine and the climate control vacuum system is completely air tight. All check valves and vacuum elements (pods) were checked and replaced as necessary. The final problem I have is that the climate control flaps remain in the defrost mode (windshield vent and extreme right and left vent are always open). The pods never change state no matter where the temperature dial is set or the push buttons are set.

All the fuses are good but I did notice something which may be key in narrowing down the problem. When i rotate the temp dial from low temp (AC compressor on) to high temp (heat starts blowing) i don't hear any of the electric controled vacuum valves (located behind the push biuttons) making a clicking sound. I do this with the fan set low so I can better hear the characteristic clicking sound when one of the valve should be energized. Some of the electric valves should change state when the system goes from AC to heat mode in order to activate the cooresponding vacuum pod (e.g. footwell or center vent pods).

I suspect the ACC control module or whatever it is that powers the switch/valves is the culprite. Does anyone know how to test this and how to get to the area that needs testing? I guess a new ACC module is expensive and don't want to start swapping parts without troubleshooting first. What can prevent the valves from functioning? What needs troubleshooting and possibly replacing?

While I'm there I would like to convert my dial from Celsius to Fahrenheit as I'm the only "scientist" in the family. Celsius along with the other SI units never did catch on in the 80's cause Ronald Reagan couldn't understand them.

Thanks

__________________
1972 450SL
1982 300D Turbo