Two problems related to wiring have been reported for the 2006 BMW 5 Series. The most recently reported issues are listed below.
A message on the vehicle display screen indicated that the right-side low beam headlight was malfunctioning. I removed the headlight assembly to replace the bulb and found the wiring insulation is crumbling to the touch, resulting in a short circuit. The headlight bulb is not actually burned out. There are many complaints about this on the BMW forums but BMW and the headlight manufacturer, hella, refuses to acknowledge the problem or do anything about it.
The contact owns a 2006 BMW 525xi. While driving 60 mph, the lights on the dashboard illuminated and the vehicle decelerated to 10 mph. The vehicle was unable to drive over 10 mph. The dealer stated that there was water on the passenger floor of the vehicle, which damaged all of the wiring and sensors. The dealer was unable to determine where the water originated, but suggested that it may have entered through an open window while it was raining. The current and failure mileages were 13,859.