OK, made some progress, but I'm not sure how or why??

I finally figured out how to check the servo motor - connect battery voltage, negative to pin 4 and positive to pin 5 of the servo for full heat, and vice versa for cooling (Thanks to George Murphy!). Servo motor runs fine. Tested the aux pump with direct battery voltage and it runs fine - started the car and now I have heat and cooling! I can also clearly hear the servo running, resetting to the Park position when you turn off the ignition. I did put the front wheels up on ramps, to try and help get air out of the system - maybe that helped. Or maybe I just needed to "jump start" the servo motor (the thing was purchased several years ago as a back-up and never installed).

Anyway, so far so good...

ryan

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RG Newell

1984 300D
1972 250
1986 560SL
1991 300CE