W124 buzzer advice?

[MustMakeAmends]

W124 '86 300E
What has to be done to silence the seat belt/ign switch buzzer? I want to be able to turn the key w/out hearing that 5sec noise. (I'll put on the seatbelt after, I promise.)

The other day, I told an indy MB mechanic to do this for me, he mistakenly thought I meant the buzzer wouldn't stop even After I buckled up, so he bridged the driver's seat belt wires and now I've lost the option to quiet the buzzer by buckling up before starting the car -which I know I had before.

The mechanic claims the buzzer is designed to always sound when you 1st start the car, whether you've buckled up beforehand, or not (no way). And he thinks that the only way to stop the buzz would also result in loss of my interior lights and electric seat functions.

Someone please tell me he's wrong, and what must be done to gain blissful silence... I don't mind losing the buzzer warnings entirely (incl lights left on & key left in ign) if necessary, but would like to find a solution that doesn't require taking the dash apart etc etc, if possible.