BMW automobiles are high-end pieces of machinery, but even the best cars can suffer a variety of problems with their audio systems. Issues can range from radios that simply won't function to speakers that emit odd sounds. Fortunately, many of these problems can be diagnosed in your own garage if you are willing to invest the time.
One problem that can arise in BMW stereos is erratic volume control. The volume may jump dramatically or drop off severely when the volume control buttons are used. One possible solution is to remove the head unit and spray electronic contact cleaner onto the backs of the controls. This gets rid of dust and particles that may have been causing the problem.
The deck's display can suffer lighting problems ranging from no display at all to just some of the functions displaying -- such as what station the radio is playing -- while others do not. This is often caused by burnt-out bulbs, broken connections inside the stereo or problems with the main board. Fixing the problem almost always means removing the head and disassembling it. Once it's apart, it can be checked for burnt-out bulbs and bad connections. Fixing a bad connection can be done with a soldering iron and multimeter to test the power.
Trunk-mounted CD changers sometimes produce erroneous jammed CD messages. First, try disconnectng the wires to the unit to reset it. If this does not work, the unit must be repaired or replaced.
If the radio displays a "code" error and does not function when the car is turned on, it probably needs to have the security code re-entered. If you've lost the code, it can be obtained from BMW for up to $65. Once you have the code, enter it according to BMW's directions. It also might help to disconnect the battery overnight to reset the car's electronics. Aftermarket components such as navigation systems can also cause problems, as crossed signals can keep the stereo from functioning.
BMWs have complicated speaker arrangements. While the range of the speakers is what makes BMW stereos sounds so great, it also means that there are more potential problems. If the speakers make scratching or other odd noises, they may simply be blown, in which case they need to be replaced. Noises can also be caused by bad connections to the speakers. Remove the speakers and inspect the connection. Reconnect any that have become disconnected and re-solder any broken connections.
