Cruise control problem diagnosis
 

My cc is flaky, sometimes it works but mostly it doesn't.
It accelerates normally when you hold up the stalk, but drops out very shortly after, often with a bit of an on-off stutter, which drives my better-half nuts, and does not contribute to harmony in the cabin! My typical highway trip (to Halifax) is an hour and a half, so it's a real pain not having the cruise.
I have taken out the instrument panel and cleaned up all connections. My brake lights are functioning normally.
What else can I do to diagnose the problem before I start ripping into bigger stuff? So far I can't find the electrical connection to the actuator unit, I suppose that's an obvious fault possibility, but where is it??!
Thanks,
Bernie
1994 E300 TurboDiesel wagon, 124193 603960, import from Japan.

In all likelihood, you have a bad amp. Usually simply replacing the amp does the trick. However, in SOME cases a bad actuator causes the amp to go bad.

Exactly my problem recently. Replaced the amp and all is well.

Thanks to Shertex and Bob338, who gave me the confidence to focus in on the amp, I now have a fully-functional cruise again. Sent it away to GDL and a good few dollars later, received it back, working perfectly. (Thanks Peter). I shudder to think what a new one would cost. It also amazes me that VDO never got their qc sorted out to produce an assembly that would last the life of the car.

Really not a QC problem. What happens is that over time, vibration and temperature changes crack the solder joints. Usually they are repairable by re-soldering. Not difficult but very tedious since there's at least a hundred such joints on those boards.