Question about 2003 BMW R 1200 C Classic

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Alternator The alternator isn't working. Also my headlight isn't working. I believe its the same trouble because the headlight relay's power is connected to the output of the voltage regulator. I don't have a manual for this bike, so I don't really know where to start. I downloaded a wiring diagram and did some trouble shooting of my own but didn't get anywhere. If anyone has any ideas that would be great. Thanks.

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How do you know the alternator isn't working? I'd check the fuses, and the bulb first - kiss and all that. First things first you gotta check to see if there's any output from the alternator, start the bike, check the voltage across the battery at idle, then at 5000rpm. It should be at least 13 volts, and should increase with rpm rise. If it doesn't you need to look for the three yellow wires leading from the alternator, set your multimeter to ac voltage. Disconnect the three wires, and run the bike with it disconnected. Now you need to check across all three wires in all combinations: AB BC CA All of them should be about equal in output. If one is substantially lower you've identified a bad coil.

Posted on Nov 20, 2008


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