Internal central lock switch stopped working on 97' A6

The internal central lock switch (in drivers door) has stopped working. Normally will lock and unlock all doors during driving or standstill.
I don't know when it stopped working, but I recently had to renew the battery. Was hoping that some sort of resetting can be done, but the instruction booklet doesn't tell anything about this.
The diagrams in my workshop book don’t show the extra switch either. But I guess it's got tree connectors like the door lock switches.
Is it easy to pop out the switch to check function?
The car isn't equipped with original alarm / infrared remote control. A DEFA alarm with remote control is however installed. Normal operation of door locks are therefore done by engaging / disengaging the alarm. The internal lock switch has worked for several years before with this setup.
Ottar Tverberg
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