So, I attempted to build a simple ice cube relay to control the AC compressor with just the ACC thermostat wheel. After that failed (I guess there's a reason why I'm not an Electrical Engineer), I kept staring at the KLIMA relay that I have from that 1991 350SD parts car. I turned it over and saw the labels on the pins --- they are the same as the 300SDL. Plugged it in and cycled the key and ACC unit and presto, I have working AC.
I did test to see if jumping "hole" 5 & 7 and sure enough that powers up the compressor without any protection.
Oh.....btw....after I turned the car off, I remeasured the resistance between "hole" 9 & 11 (speed sensor) and measured 707 ohms. I'm guessing the range of 530 to 650 ohms is a cold measurement.
So, it looks like my existing KLIMA relay was the culprit.
Anyone want to give me a lesson in reading/interpreting the KLIMA relay diagram?
