Is there any way for the home mechanic to check the condition of a cruise amp?

I ask because today I decided to tackle the non-functioning cruise on the 560. When I say non-functioning I mean absolutely nothing happens when you try to activate the cruise. My sources tell me with that symptom the cause could be anything and trouble shooting begins.

I started by checking the actuator, it works - motor turns in both directions, nounusual noise and only a very slight whirring sounds when power is applied to pins 4 and 5. Current draw is ~137mAmps. Puting power to pins 6 and 7 activates the solenoid.

I pulled the cruise amp and swapped it for the best looking of the three I grabbed up at the salvage yard. Easy enough to get out, but a bugger to get back in. No one has mentioned about accidently knocking the bolt from it recess. What a PITA to get back in place, and hold there while mounting the amp. Anyways, got the amp in and went for a drive.

Now when I activate the cruise, the ccruise will engage and accelerate the car. Soon as I let go of the stalk, the cruise disengages. Symptoms point to a bad amp. Well, the old amp was shot, or was it? Maybe my dinking with the actuator cleared the problem and I swapped out a good amp. No, I didn't test the system further before changing the amp.

If there is a way to verify the condition of the amp, I can check the original out, as well as the remaining amps I have on hand. Maybe I could even have cruise by the time I head to Lost Wages at the end of the week.

__________________
Mike Tangas
'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.