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Thread: R80RT Generator Light

  1. #1
    Registered User coyotebmw's Avatar
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    R80RT Generator Light

    I have a 1983 R80RT with a strange problem and want to know if any other R80 owners have seen anything similar. In the mornings when I start the bike up and start riding it in the dark the Generator light glows very faintly. When I come to a stop the light goes out, but as soon as I start up, it starts to glow again. I have had the entire charging system checked out by the BMW shop and except for adding a new ground strap to the diode, they could find no problems. Anyone ever hear of this type of problem before?
    CoyoteBMW
    53 years of BMW's - 1960 R26 and 2007 F800ST!

  2. #2
    Cannonball Rider #52 darrylri's Avatar
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    Typically when the charge light glows faintly while the motor is well above idle, it means that either the diode board or the alternator rotor is about to go south.

    But it shouldn't matter whether you're stopped or not. When you say you're stopped, does that mean that the light goes out when you've got neutral selected? Or that you're holding in the clutch and/or front brake lever? If any of those is the case, you might have a grounding problem in the instrument cluster.
    --Darryl Richman, forum liaison
    http://darryl.crafty-fox.com

  3. #3
    Registered User coyotebmw's Avatar
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    That is what I heard from the BMW dealership. That is why the charging system, diode board and generator were checked out. All checked out OK. The only thing they did was replace the ground strap on the diode board. After that they said the system checked out as having a strong charge. As to the light going out when stopped, that seems to be related to the bike going to idle more than anything else. In the process of the dealership working this problem the instrument board was replaced as well, because of a neutral light that wasn't working.
    CoyoteBMW
    53 years of BMW's - 1960 R26 and 2007 F800ST!

  4. #4
    Club President Emeritus chrishea's Avatar
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    Lightbulb Glowing Generator Light

    I don't think anything is about to fail, but some ground isn't grounding well. There should be a ground wire that comes down from the instruments and ties into the frame on one of the brackets under the tank that holds the coils, ignition box or voltage regulator. Oftentimes this ground gets corroded and doesn't ground as well as it should. Remember that grounds are brown on BMWs.
    Chris

  5. #5
    Registered User coyotebmw's Avatar
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    Thank you

    Thank you Chris, this sounds like what I have started to suspect. Because of the way the glow seems to be related to the engine RPMs, i.e. when the engine idles the light goes off, when I accelerate it comes back, I have been thinking it is a ground of some kind. I will check the ground out tonight.
    CoyoteBMW
    53 years of BMW's - 1960 R26 and 2007 F800ST!

  6. #6
    Registered User jgr451's Avatar
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    I have a1984 R100,sounds like the same as yours.I had similar mysterious goings on until the diode board finally showed up fried.I recommend you buy a replacement and learn the re and re procedure,sounds like that is where you are headed.Only trick I recall was the cushioned mountings,difficult to fasten and unfasten undamaged.
    If I were not mechanical and planned to be where stranding would be awkward,I would change the diode board.The new improved ground strap is only part of that problem.

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