My unit is still not funcitoning - i've tried soldering hte joints that look non-perfect.

I found this though on the net - worth posting in case it's of help.

http://www.m-100.de/Schrauber/Schrauber.html

try bablefish to translate.

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i'll cut and paste but there picture may not come thru and is essential ....................................................................

2. Repair of the Tempomatsteuergeraet in the W116

One of the well-known problems with the 116er is that the Tempomat stops gladly times its work (also 123'er suffer gladly from this problem)
The symptoms are then in all rule those that one can accelerate and/or retard with the lever at the steering wheel, but the speed is not held. The Tempomat suffers as it were from Amnesie.
The reason is in the majority of the cases in the controller to search (approx. postcard-large aluminum box with 10-poligem plug at the brake pedal suspension).
On the plate sit eight electrolytic capacitors, which are responsible among other things for the "speed memory". An unpleasant characteristic from Elkos is to drain with the years. They work then depending upon ambient temperature more or less (usually less) reliably. That is also the reason, why the Tempomat functions times, and times not. A new controller brings naturally remedy, but first of all "pig-expensively" and secondly represents it is not for people with "soldering hands" a problem to renew the Elkos. The most difficult is still to get the partly exotic values.

The parts on the plate are marked by 1 to 8.

It acts over:

Nr.1:..15uF 10V tantalum

Nr.2:.2,2uF 35V tantalum

Nr.3:.1,5uF 25V tantalum

Nr.4:..10uF 16V tantalum

Nr.5:.2,2uF 35V tantalum

Nr.6:.4,7uF 10V tantalum

Nr.7:..47uF 16V standard

Nr.8:..47uF 16V standard


The kapazitaetswerte refer to the controller MT 001,545 2032 and/or. 412.203/1/3 VDO 117509 116 2.80. from the 6.9er.

Since there are evtl with the different Fz-types also different controller tunings, please values before replacing examine! They normally stand drauf. Than on the original Elkos indicated higher values for the tension strain (e.g. 35V instead of 10V), one cannot insert, lower better. On the plate in each case a small + indication is by the solder tack on the back (partly badly identifiable, if over-soldered). That is important, because wrongly soldered Elkos behaves possibly like small bombs! Plus with (new) the tantalum beads is right, if one sees on the writing and the legs downward to show. With the Standardelkos is imprinted + and -. Most kapazitaetswerte are with "Mr. Conrad" to gotten, thus Exoten like 1.5 and 15uF know he not only. They are however in the radio and television engineering common. Not to get if, one can join in parallel if necessary also two values, e.g. 1uF + 0,47uF replaced then the 1,5uF. Since with not selected Elkos tolerances are usual around the 20% like that, the not completely correct value is negligible. Best few a more buy, through-measure and they combine in such a way that they come the original value next. The tension strain should be naturally identical then. Unfortunately the plate is factory-installed provided with a protective varnish, which lets a soldering and the optics of the new solder tacks become a pure pleasure...)

With the in such a way repaired controller the Tempomat should do actually again its service.

I point out again expressly that it does not concern a workshop manual here! This paper has an only informative character. All data are without guarantee. The author excludes an adhesion for damages by interference into a controller expressly!
Jens B.




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anyone tried the fix - i.e. change capicitors? how do you tell if the ones you have are tosted?

I managed to make my controller even worse after just using a circuit tester on it.
So after that I just s-canned everything related to the cruise control. It made the engine look a little less cluttered too.

__________________
DJ


84 300D Turbodiesel 190K with 4 speed manual sold in 03/2012

Also - try ...

http://64.233.179.104/translate_c?hl=en&sl=de&u=http://www.sternzeit-107.de/modules.php%3Fname%3DNews%26file%3Darticle%26sid%3D248&prev=/search%3Fq%3D412.203%2Bvdo%26hl%3Den%26lr%3D%26client%3Dfirefox-a%26rls%3Dorg.mozilla:en-GBfficial_s%26sa%3DG

That page makes it look easy. Now I need to find my controller in my junk bin.

__________________
DJ


84 300D Turbodiesel 190K with 4 speed manual sold in 03/2012

If good english translations where made and all recent information gathered into a sticky there would be far more working cruise controls. I think tantulaum capacitors where fairly new when these cruise controls where manufactured to start with. They may not have known of short lifespan or perhaps production reliability at that time. I think with a little help and a really good sticky perhaps even guys that have never done electronics could recondition their cruise control units properly with some guidance. At least from what I can observe so far the i/cs (intergrated circuits) do not appear to be failing. It may be less than 20.00 in parts will do a general recondition and upgrade.

A decent L/C meter would let you hand select component to a tighter standard than the nominal +/- 10% or worse many have... surplus stores if any are near you that have bins would be the best place to shop. Back when I was doing R&D work we had to do that at times in house.

__________________
Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
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Section 609 MVAC Certified
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"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche