We just purchased a 1988 E300 for our daughter. Nice car. At night, when the lights are on, most of the interior lights (gearshift, window switches, dash switches) turn on only when the volume of the bass is high. A "thump thump, thump" in the low frequencies will produce, you guessed it, three on/off cycle with those lights.

It's obvious that the lighting wiring has been cut into and some sort of device has been placed in-line, feeding off the stereo.

My question is this: Would this be in the wiring behind the in-dash stereo unit? Somewhere else? Has anybody seen this before and have any advice on how to turn this "feature" off?

Thanks!