Well, at first. Eventually with time it started to get spastic. It would work for awhile, then it would start jerking on the throttle in a most annoying manner. Eventually it would drop out. Really it was quite unusable. It stayed this way for nearly a year. (Since we got married and had a baby, we don't take many long road trips anymore. And when we do, it's usually in the truck/camper combination.)
This problem was the motivation to fix the Chicken Wagon's cruise control, as a practice measure. With the success of this job, and with a free morning looming I decided to finally tackle it.
I'm getting good at this! I had the amplifier liberated from its nest in no time, and sitting on the bench in the test harness. (A spare cruise-control system.) Upon engaging the system it seemed to work, but if I flexed the board a little bit it cut out. Yup, this one has bad solder joints written all over it. So I did the now-standard paint stripper thing, and the varnish crinkled up and washed right off. The joints on this board didn't look that bad, but the symptoms were indisputable. I fired up the soldering iron and went to work.
Resoldering was straightforward, but as always, tedious. After I finished up I gave it a good visual inspection. I retouched a few joints that still didn't look that good, and then put it back into the test harness. It operated normally, and was no longer sensitive to board flexure or tapping. I then slipped the board back into the case (it had been left mounted in the car) and went for a test drive. It worked properly, so I came back home and buttoned the car back up.
An interesting thing about this board was the 1993 date codes on the IC's, though it was out of a 1986 car. Obviously it had already been replaced at least once. And the new board wasn't really all that old to have started failing. VDO definitely has a problem making these things! Another interesting thing is that it's a longer board, with one more IC on it than the 1983 cruise control from the Chicken Wagon. All I can really say is that it works very well, better than I've experienced in any other car. (Except my 1986 560 SL, which probably has exactly the same system in it.) This makes five different VDO cruise control amplifier designs that I'm aware of, there are probably more.
I was feeling so good about this job going so well that I actually washed the car, and I even put some wax on the hood. (All I had time for, and the place that most desperately needed it.) I had started at about 5:30, and I was done with all this by 8:00, so I could clean up and go to work. Not bad for a morning's effort!
