The cruise on my '80 450sl (45,000 miles) seems to work fine with one exception. It continually loses speed over a long time. As an example I will set it at 65 mph and over the next 50 miles it will be down around 62 mph. Once I speed up and reset it it does the same thing. Not sure how far it will drift down but it is a bit annoying.

Is there a setting or potentiometer somewhere on the control unit that will get it to stop drifting like this?

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Jim Loseke
1980 450Sl

This is one of the most common failures of the early VDO controllers. We have fixed many of those controllers through two techniques; first resoldering the PC board and second replacing the capacitors. The capacitors are involved in the memory/timing sections.

Many of the rebuilders of these units add potentiometers to trim that function and a couple others; point of set and length of feedback loop.

I would also adjust the slack in the control cable as these are often very loose, which places the actuator at its end of stroke; where it has less control.

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Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician

Steve,
Is there any source of information on how to add the potentiometers to these circuits?

During the "Warranty Days" of my car, the problem was supposedly cleared up by adding temperature compensating components to the circuits. It helped but didn't completely solve the problem.

TIA


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Ted
1979 240D
160,000 miles

Years ago (about 12 I think)someone wrote a technical manual for that controller and it was printed in a "Star" magazine article. A customer brought it to me and we have used it to diagnose those controllers ever since in our radio/electronics room. Last time I saw the document it had a big section eaten out of the text (mice, I think).

I don't know if they have archives, but if any of you super sleuths can locate it, I would like another copy.

In the mean time I will see if I can locate whats left. Unfortunately my brother has the info in his hard head instead of his hard drive so I don't think its recoverable at this end.


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Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician