Help! '86 560SL cruise control

My '86 560SL cruise control acts like it is not getting any power.
An eariler suggestion was to resolder the amplifer. I removed the board, and there were too many solder points for me so I didn't heat up the iron.
I was able to read signal changes with my volt meter on the connecter to the amplifer when I operated the cruise control switch. The board's solder connections looked OK so I put it back.
What does the actuator look like and where will I find it? Maybe it has a bad connection?
Thanks,
Joe
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