Although I don't know it for sure, I suspect the unit in my car was done by Performance Analysis. I tried the number, but George is on vacation right now.

In the meantime, I still want to go through the diagnostic procedure and pinpoint the fault, and one thing that has been tripping me up is the portion that says to apply +12V to one terminal, and -12V to another to check the operation of the solenoid. I read this as a total potential of 24 Volts, and that just doesn't sound right. Do they mean +12V and ground - that would make a lot more sense to me.

Once I sort out how much voltage to apply, I expect I'll know more about the health of my servo. But I don't want to fry my servo in the process of testing it.