My car has the BMW business radio cassette & 6 disc CD in the boot. Ever since i have owned the car, i've had this really annoying problem that when i turn on the heated rear window, the radio reception goes and i cannot listen to the radio. When the heated rear window is switched off, radio comes back on! There is no effect if the ignition is switched on but no engine running. So i decided to get into it and removed the 2 c piller trims to expose the amps. I changed the passenger side one as my best guess and did nothing. Still the same. So attention was turned to the drivers side unit. I found that if i removed the supply plug from the unit, all was working fine. If i connected it back up, i get the interferance again. So the plug remains disconnected and all is working.....Go figure...I assume this has disconnected the heated rear window? Anyone got any ideas or advice? What is the unit behind the right c piller....heated rear window module or something?