cruise control on 300CE

[noeldavis]

I have a 1989 300CE auto with 144000 miles. A couple of years ago the cruise control started switching off intermittantly. Apart from this, it worked normally. This got progressively worse until it packed up completely. I've tried substituting another second hand control box but it still wont play. Of course, I can't tell if the "new" control box was any good.
Any got any ideas? Can any one tell me how the system works, or recommend service literature.

 

[piestore]

cruise controll

hi
your fault could be virtualy anything take it to a dealer or specialist to get the fault codes read out likly culprits are:-

Brake light switch
wrong tyre size or worn tyres
speed sensor fault
corroded speed signal ring
cruise relay
cruise switch
Throttle body
control unit
wiring loom

 

[talbir]

It is likely the Cruise Control Amp, which are notorious for suffering from bad solder joints.The old one you have tried may coincedentally have the same problem.

Open up the amplifier and inspect for bad/dry solder joints.

Could possibly be the cruise control stalk that is shorting on the 'off' connection. You'll need to remove the steering wheel to inspect the connections at the stalk.

OTherwise, it's only the actuator that could be faulty.

It is unlikely to be anything related to worn tyres, brake switch, speed signal, or throttle body.

 

[piestore]

cruise

Hi

Talbir why is it unlikley to be
"anything related to worn tyres, brake switch, speed signal, or throttle body." In my experince the brake lights switch is the single most comon cause of cruise failure I fit 3-4 per week and on older models the software was unable to cope with worn and new tyres on the same vehicle, and speed signal failure is also very common

Please noeldavis let us know what the problem was.

 

[Andy]

Hi all,

Trying not to step on any one's toes. But this is an early system. Made up of mainly four items.

No fault codes are able to be read. This is because its before this technology was introduced.

Main problems are usually, actuator stalk, main ecu, & actuator in engine bay. The MB test is to fit inline a test box, which test all components out side the ECU. If the test proves negative then the ECU is at fault. 1hrs labour. If your local specialist has the tool or your dealer.

Other wise best guess is the ECU or actuator. They are usually the main culprits. If its the stalk you can usually tell if its broken. It wobbles a little too easy. But to be thorough, then the MB test every time.


Regards


Andy @ www.mercedesservicing.com


The test also checks the brake light switch. Although they are much more reliable than the later stuff.


So much for NEW tecnology. I can hear you all say."They don't build em as good as a 124 any more". Guess what? Your right!!!!!!!!