How to Test a BMW Diode Board

1. Use an adjustable wrench to remove the motorcycle's negative battery cable.
2. Access the diode board and remove the electrical connectors running from the stator and alternator. Also use a screwdriver to remove the screw holding the diode board in place.
3. Set the diode board on a work bench.
4. Turn on the multimeter and turn it to the diode test function.
5. Place the positive lead of the meter to the anode lead of the first diode and the negative meter lead to the cathode lead. The cathode lead of the diode is the side marked with a single band on the body. Examine the reading, which is the voltage across the diode. Reverse the meter leads on the diode connection. If it registers any voltage across the diode the diode is bad. Check all the diodes on the diode board in this fashion. If three or more of the diodes are bad, swap out the diode board with a new one.