What's the most common to fail with Tempostat (cruise control)

[Muf]

Hello everybody,
I am experiencing a problem with the cruise control. It does not keep the speed. I can hear clicks in the control unit when moving the controller but that's all.

Is the unit the most likely place to go wrong?
I have disassembled it and cannot see any visible problem (yeah, I know, most electro-related problems are invisible :-)).
Or maybe the wiring? There seems to be something magic related to my car's electro instalation, anyway :-)
Corroded cables? I do not know
Has anybody experienced similar problems with the Tempostat?

P.S. I have an european 79 SC targa, about 170 kkm (cca. 100 k miles)

[Wil Ferch]

Do be careful...in Porsche's infinite wisdom, the unit fails "high"..meaning the car picks up speed...instead of failing "low" ( like it's disengaging).....

Clever Germans ! ......


-Wil

[Muf]

Well, I should be happy, after all :-) that the cruise control is non working the way like if there was none....

So should I untestand it that the unit is not the thing which is bad?

[Wil Ferch]

I can't say for sure if there is still a problem with the unit itself or with the wiring and control units that may be attached to the "box".

I simply recalled that an often-mentioned failure mode is that a car picks up speed instead of failing by losing speed. Obviously you have some other problem that I can't speak to. In all electrical issues, I usually go after ground quality first. most often, it's related to bad grounds. In those cases were it isn't, ...well...at least you have good grounds as a baseline to go from..and your grounds are good for the foreseeable future as not being a problem area.

Wil