600 has an unique issue, of the microswitch failing. The system as designed by MB is over engineered. As you close the door to the first notch, a microswitch sends a closure signal to the pump which starts and puts pressure down the line to the actuator, there are two sensor scenerios, the actuator closes the door and the and the microswitch tells the pump to shut off, parallel to this circuit is a timing cicuit which has a predetermined time to see the micoswitch closure or the pressure sensor. If it does not, in two repeated attempts it diasbles that line. These failures are as follows, the pump due to age slows down and the timeout takes effect, the lock is stiff and it takes more time or pressure for the switch to signal "task complete".
I having gone thru this and about to put in pump #3 decided to take the adjust the pressure device, give the sensor a minor adjustment (one turn or less) and you should get good results.
I thought I knew everything but this is a excellent write up, and always took the easy way. I spoke to the "guys at MB and they concurred " but in no way could they attempt this remedy in anything other than personal cars.
Pulling fuse #9 resets the system but not for long
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