Mercedes-Benz W140 central locking vacuum pump not working
300 S300 SE 3.2350 TD500 S
W140 central locking and trunk lid do not work, which pump operates them?
The locking, trunk lid and suction doors work on vacuum, which is produced by an electric pump under the rear seat. If all of these stop working at the same time, suspect the pump first, its fuse or its electrical supply.
How can a W140 vacuum pump fault be located?
First check the fuse and whether the pump gets power. If the pump whines or only clicks, the fault can be in the pump motor, for example worn brushes, or an air leak. The pump also stops trying after a few failed attempts.
Why do only some of the doors stop working on the W140?
A door usually stops working first at the end of the longest hose when there is a leak in the vacuum. Go through the hoses one by one and see whether a hose or joint has come off. Stiff locks or a weak battery can also prevent operation.
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