Cruise Control and Speedometer...

[aeklo]

Hi!

My car: MB 230CE w124 '87.

My cruise control will kick in only occasionally.
And when it does, it surges all the time. Not that much that you can see it on the speedometer, but you can very well feel it. Less noticeable uphill.

I also noticed that my speedometer needle surges up to a speed of approx. 35 km/h (40 km/h is the min. speed for C/C). Could there be a connection there?

Perhaps the needle damps the surging when passing 35 km/h, but that the cable still is actually surging? And thus making the C/C amplifier confused?

And, if so, will this be the reason for the C/C only operating occasionally? (It seems to either function or not function for each engine start, ie. if it does work, it does so until engine shutdown).

By the way, is the speedometer in my car driven by a cable (mechanically) or electronically?

I really would like to sort this out, and appreciate all help you can offer!!

Anders Eklo - Norway.

[Edited by aeklo on 07-25-2001 at 10:04 PM]

[Stan Pittman]

The speedometer is cable driven and if it's as you say up and down surging this would fool the cruise control. First thing I would suggest is to replace the speedometer cable and get your speedometer operating correct. That may solve all of your problems if not all dealers and most independents have a cruise test tool that can pinpoint the problem.