What does that all mean?
Are you saying that the defrost position bypasses all related electrical imputs and immediately moves the servo motor to allow coolant flow to the core regardless of any other setting? If that being the case should I look at the servo motor as being defective? Is the input to the servo electrical or vacuum operated to cause it to move? I noticed two seperate vac lines going to it from the bottom, I think one was yellow and the other black. Do these have a direct input on servo motor movement?
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'84 300SD 256,000 Gold on Brown (Mileage Award)
'86 300E 246,000 Blue on Tan