When you put power to the actuator, the motor should spin with a barely audible whirring sound. Sound not make any loud clunking or grinding sounds. You need to be sure to run the actuator both directions (by reversing the power leads). Mine was so quiet I had to put my hand on the actuator to feel it spinning. Power to the solenoid should produce a solid clunk as the solenoid engages. I didn't try seeing if the arm moved, I trusted the spin and clunk. Once I replaced the amp the cruise works great.
If all is well, I'd bet on a bad amplifier.
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.