It is cause by the failure of a small sp.
Mercedes a class door lock fault.
Mercedes benz keyless go entry door exterior handle push lock button square cover rubber plastic repair kit install instructions.
C class drivers have described the problem as electronic door locks that function properly when activated remotely however when the doors are actuated from inside the vehicle they fail to lock properly.
If you find a blown fuse replace it.
Depending on the mb class this fuse can be found in one of the fuse boxes located in the engine bay side of dashboard under rear seat or trunk.
You likely have a shorted door lock actuator which you can replace with a new unit for the lock that is not working.
There is a couple of ways to fix this problem.
Mercedes benz vehicles such as e c s ml gl r class are designed to automatically lock the doors as soon as you start to drive.
Bouncing door lock is a common failure on mercedes cars.
Because your mb receives the lock unlock signal via the antennas installed on your car a bad antenna module fuse can also cause mercedes key fob to stop working.
On those models the door lock actuators may fail causing the door lock to bounce up and down several times.
With its varied options for technological conveniences a major inconvenience some c class owners have found is door lock faults on their new c class mercedes vehicles.
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Apply wd 40 or equivalent product directly into the lock.
Open and close lock to recalibrate.
Perhaps your mercedes locks work but they open and close slowly.