Cruise Control De-Activates

atttim

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MB SLK 230 Kompressor Model Year 1999 and a Suzuki Alto FX Automatic Model Year 1985
SLK 230 Kompressor Year 1999
When the cruise control is activated, it automatically disengages at approx 78mph, always when the engine comes under load eg. when starting to climb even a mild hill/slope
It will not re-engage at any speed above approx 80 mph.
Providing i stay at approx 76 mph it will maintain this speed at ALL times with no problems.
I use this car in germany quite a lot hence the use of the cruise control above 70 mph !!!!
 

television

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Hello and welcome :D:D

Not an easy fault,,as it is speed related, I would check the cleanliness of the wheels sensors first. Are the tyres correct for the car
 
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atttim

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The cruise control has been working fine for the 3 years i have owned the car fitted with the same size wheels and tyres since i have had the car.
I will check the wheel sensors.
Where can i obtain a Wiring Diagram of my car so i can do some basic checks myself ??
 
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atttim

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By the way...i dont understand the term PM's written in red on your page.....am i asking about my fault in the wrong section....??
 

Alex Crow

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i suspect television is heading in the right direction. i would be looking to do a live data check on wheel speed values at 80+ mph. sadly this would leave me liable to prosecution so a blast at 70mph on the dual carriageway would have to do.

if any doubt about all 4x wheel speeds, cruise control cuts out first - before any braking/traction/stability systems light warnings.

PMs are private mails, you are in the right place attim.
 
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atttim

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...i'm afraid you got me there...about the television heading in the right direction....a little too subtle for me that one.....but got the gist of the rest.....

So is there an "idiots guide" or Workshop Manual covering the operation and testing of the cruise control that is available anywhere for the likes of a mere mortal like myself...??
 
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atttim

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oh my goodness....the penny has dropped !!! TELEVISION Senior member.....I really am thick after all !! lol
 

television

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By the way...i dont understand the term PM's written in red on your page.....am i asking about my fault in the wrong section....??

You are doing perfect,,do not worry:D:D
 

nickcc101

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This may not help but on my W203 there is a setting for max speed that can be changed using the steering wheel buttons. I presume this is for different tyre ratings but not sure, if it's set too low, if it knocks out the cruise control. Just a thought and i may be on the wrong track,
 
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atttim

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Thanks for the above info...yes my car has both Cruise Control and Speedtronic and i have carried out the instructions in my user handbook to deactivate the Speedtronic in case it had been inadvertantly engaged but i can confirm that it is not enaged.
Thanks Television for that Parts Diagram.....those shown would appear to be the sensors relating to the braking system which if faulty i think would affect my braking which appears 100%.
The throttle cable seems to terminate at a smallish Potentometer/electric motor, with no apparent further attatchment to a mechanical throttle components ! Hence the engine speed would appear to be controled electrically by the ECU ? So, does a signal from the engine speed sensor via the motor/potentometer to the ECU control the on /off mode of the cruise control ?? Possibly a visit to my local MB agent will be unavoidable without the magic "box of tricks" which often seems to be the norm once basic hand and eye checks have been done by myself.
 

LYNALL

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Before we had all the posh test equipment, we used to jack up each wheel pull the sensor plug set multimeter to volts (cant remember dc or ac) spin the wheel at a steady speed, watching the readings change, what you are after is a nice steady reading, common problem was dirt in the gaps in the exciter rings quick clean and all was good, another problem was runout ie a slack bearing, also another was a weak signal ie sensor to far away from the ring.

Most were fixed by cleaning the ring and resetting the sensor.

Not sure on your car but wifes front exciter ring is built into the front hub seal.



Lynall
 

television

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Though the same sensors are used for ABS the CC is much more sensitive to any speed change
 

martin.mercedesclub

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I have the same issue I think... W210 EClass E240. Cruise all day at 72, but set the cruise at anything above that and it runs for a mile or so then drops out. Once it has dropped out it cannot be re-engaged without an engine restart. (a bit like a pc :-( ).

A further bit of info is that once it has dropped out if you attempt to switch on the speedtronic max speed system you get an error instantly saying "speedtronic - visit workshop". Iv'e been into the main dealer a dozen times - - THey have no idea what is causing it and don't seem to be able to find the problem :-(

Anyone heard of this before?

Thanks,
Martin.
 


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