| RE: Restoring function to your closing assist pump. Adjusting the pressure shut-off. Long w/pics.
Bret,
Great description: According to MB140 CD service info the pump starts when the first microswitch in the door indicates it is in position one. The pump creates pressure until it gets a signal from another switch (or maybe the same microswitch that tells it to shut off (the door or trunk is latched)if it does not, the limit switch should open to keep the diaphram from rupturing. I think there is a timing circuit to keep it from running too long (I am not definate on that) The two or three tries (are fact) that it does disable the circuit untill the power is removed to reset the circuit. The bulletin refers to the vacuum porting as purging the lines. You will notice the doors and trunk close beyond the catch and then relax as the pressure is removed and vacuum is introduced. You can normally hear the vacuum release in the trunk where the relif hose vents. I believe if all the doors are slammed at the same time the pump adresseses each in order, that way it knows when one fails to close.
Great diagnosis, I took one apart and it is another example of over engineering by MB.
The "locking pump" is very similar in providing pressure and vacuum for doors, orthopedic, and engine vacuum for HVAC system. |