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  1. #1

    Charging Question

    Good morning electrical wizards-

    I just replaced a failed battery and my voltmeter is showing no charging taking place. Readout is 12.8V after being on the battery tender all night the. It steadily drops to 12.1V while Iím riding. I shut it down at this point. The battery warning light never lights up indicating charging.

    Ive checked and cleaned all connections, replaced the voltage regulator, checked brushís and contacts on the alternator and diode board. I just noticed the battery warning light does not come on when I switch the key on so Iím suspecting a burned out bulb. Reading Snowbumís site this should not prevent the battery from charging unless Iím reading this wrong.

    Any ideas?
    Thanks,
    Charlie
    Charlie P.
    1992 R100R

  2. #2
    Rally Rat 1074's Avatar
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    Charge light

    I think you're reading it wrong. If you turn the key on you should get a light. If you don't then you need to troubleshoot. Pull off the front cover and ground the rotor slip rings. If the light comes on while grounded then you have an open rotor to replace. If no light then take apart the instrument pod and check the light bulb. Do this in the socket because sometimes they corrode (the socket) so that you lose continuity.
    Once you have the charge light coming on with the ignition start the engine. The light should go out around 1500-1800 rpm. indicating that the system is charging. Running a volt meter across the battery will tell you how well it is charging but that's an answer to another question.
    Boxerbruce

  3. #3
    Quote Originally Posted by 174713 View Post
    Good morning electrical wizards-

    I just replaced a failed battery and my voltmeter is showing no charging taking place. Readout is 12.8V after being on the battery tender all night the. It steadily drops to 12.1V while Iím riding. I shut it down at this point. The battery warning light never lights up indicating charging.

    Ive checked and cleaned all connections, replaced the voltage regulator, checked brushís and contacts on the alternator and diode board. I just noticed the battery warning light does not come on when I switch the key on so Iím suspecting a burned out bulb. Reading Snowbumís site this should not prevent the battery from charging unless Iím reading this wrong.

    Any ideas?
    Thanks,
    Charlie
    Thanks for the quick response! I think the charge light just started not coming on so I checked the battery voltage at 3000 rpm, no charging taking place. Would the bulb/bulb holder malfunctioning prevent charging?
    Charlie P.
    1992 R100R

  4. #4
    Registered User ebeeby's Avatar
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    Yes, the bulb must be functional.
    1973 R75/5

  5. #5
    Rally Rat 1074's Avatar
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    Check the rotor first! It is the easiest to do and is much more likely to be the problem.
    Boxerbruce

  6. #6
    Quote Originally Posted by 1074 View Post
    Check the rotor first! It is the easiest to do and is much more likely to be the problem.
    I checked the bulb, itís good. I checked the bulb socket, also good. Connected the VOHM meter at the socket, turned the key on, got 12.6V. Put the bulb back in the socket, turned the key on, no light. Did this 3 times and got 12.6V at the socket but no light. Swapped out working bulbs to this socket, still no light.

    Any other ideas?
    Charlie P.
    1992 R100R

  7. #7
    Liaison 20774's Avatar
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    Charlie -

    Somewhere down the line, you should probably invest in the Boxer Charging book offered by Motorrad Elektrik. You can carry this with you to troubleshoot the charging system.

    It sounds like your problem is downstream in the alternator. The rotor was mentioned...it is the weakest link. But you must take steps to isolate the problem rather than just throw money at it. Read this section from Snowbum's site:

    http://bmwmotorcycletech.info/trbleshootALT.htm

    This will step you through things to identify where the problem is.
    Kurt -- Forum Liaison ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

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