Next to the light switch on my 500e in a plastic button with a red light above it. Being a curious sort, I worked up the courage to actually push the button. It did not activate an ejector seat, fortunately. It makes a beep like sound. If I hold the button down for awhile, the button flashes red for awhile and then yellow. I've never seen the red light above the button light up. I sort of assumed that it was some kind of after market alarm, radar detector, or possibly asr defeat switch. But it doesn't seem to do anything. Any ideas would appreciated to verify it's function.

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1992 Black 500e
1991 Black 300te 4m
1992 Black Renntech 620sl
1979 Porsche 911sc targa