OMG! I had a total catastrophe with this thing. I borrowed my friend's iPOD for the trip I had to make in my new 99 C 280 from Chicago to San Antonio, where I live. I discovered the same thing you did. What I found is that if you plug the sensor, it will be on the right side of the fold down screen on the unit, not on the screen, it will quit the annoying beeping sound. But you have to make sure you plug it good cause that sucker is stronger than you think. Don't try to shut the screen cause you could end up doing what I did and break the damn latch that holds it up there. I did that and ended up super gluing it shut cause A. the tape adapter's appearance sucks with that screen down all the time and B. The sound was freakin' terrible and C. I don't use cassettes anymore so I wouldn't miss it. I ended up changing the head unit cause it's a hell of a lot easier.