RTH zero ohms also means no adjustment
I kind of figured the sensor being unplugged defaulted the valve into the heat mode only as there is no temp control at all with it unplugged, only heat. You're right, at least I know my heating valve is working. Now if I can just figure out what isn't I'll be fine. I think I'll ohm out the ambiant temp sensor next and then if that pans out alright I'll try the temp dial to ensure it's set correctly. If you have any other easier ways, let me know.
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'84 300SD 256,000 Gold on Brown (Mileage Award)
'86 300E 246,000 Blue on Tan