Erratic cruise control
06-27-2003, 10:50 PM
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1992 300E
Erratic cruise control
When use the cruise, it constantly "pulses" the motor. After 5 minutes or so, it will just disengage for no reason. Any ideas where to start?
06-29-2003, 09:08 PM
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02 W163, 84 W123, 03 E39, 98 E39
Cruise Control Problems
I have owned three W-123 MB's (83 240D, 84 300D, & 84 300TD) all that had problems with the CC similar to what you described with your W-124. I don't know if they improved the CC with your model, but my experience with CC problems is as follows:
In the W-123 the CC has two main parts. There is a computerized control box under the dash and a mechanical actuator mounted to the top of the engine. Either of these two parts can go bad and cause the symptoms you describe. In the past, what I would do is take a part from one of my cars where the CC was working fine, and swap parts until I identified the defective part. Now, none of my CC parts work, so I just gave up. These two parts are expensive if purchased new from a dealer (old prices $250 to $350 as best I remember). Less expensive parts can be located on the Internet by using googel and typing "mercedes benz parts".
One inexpensive thing I did many time to solve this problem was to dismount the actuator from the engine and then take apart and clean the actuator. Inside my actuators is a copper contact that a wire attached to the actuator shaft contacts. As the wire goes around in an arc touching the copper contact, the actuator keeps track of how much throttle it is giving the engine. The copper contacts get coated in grease and grime and the "contact" between the wire and the copper contacts gets compromised. Cleaning the grease and crud off the copper and the wire many times solved CC problems. If you decide to dis-assemble the actuator, be careful as you take it apart as you need to remember how the parts go back together.
Good luck.
In the W-123 the CC has two main parts. There is a computerized control box under the dash and a mechanical actuator mounted to the top of the engine. Either of these two parts can go bad and cause the symptoms you describe. In the past, what I would do is take a part from one of my cars where the CC was working fine, and swap parts until I identified the defective part. Now, none of my CC parts work, so I just gave up. These two parts are expensive if purchased new from a dealer (old prices $250 to $350 as best I remember). Less expensive parts can be located on the Internet by using googel and typing "mercedes benz parts".
One inexpensive thing I did many time to solve this problem was to dismount the actuator from the engine and then take apart and clean the actuator. Inside my actuators is a copper contact that a wire attached to the actuator shaft contacts. As the wire goes around in an arc touching the copper contact, the actuator keeps track of how much throttle it is giving the engine. The copper contacts get coated in grease and grime and the "contact" between the wire and the copper contacts gets compromised. Cleaning the grease and crud off the copper and the wire many times solved CC problems. If you decide to dis-assemble the actuator, be careful as you take it apart as you need to remember how the parts go back together.
Good luck.
