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Thread: Charging Question

  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!

  8. #8
    Quote Originally Posted by 20774 View Post
    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.
    Hi Kurt-

    Thanks for the insight, I purchased Rickís book then lost it in our last move. Iím ordering another copy today.

    Iíve gone through Haynesí troubleshooting steps, voltage regulator, alternator, diode board are all good. Iím down to the dash bulb and saw Snowbums comments about failures there.

    What I canít understand is why Iím getting voltage at the dash bulb socket when I turn the key on but the bulb does not light up. Next thing is to call Rick.
    Charlie P.
    1992 R100R

  9. #9
    Rally Rat 1074's Avatar
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    dash socket

    Often you'll get power on the board but no light. This usually means that the bulb socket is not making full contact with the thin metal tape that fits in the hole that the socket fits into. Sometimes it is corrosion on the metal tabs on the socket where they contact the thin metal from the board. Sometimes the thin metal from the board isn't stuck down the hole that the socket fits into. Sometimes there is a hairline crack on that thin metal tab and the contact point with the socket tabs is not through to the rest of the board.
    Boxerbruce

  10. #10
    Quote Originally Posted by 1074 View Post
    Often you'll get power on the board but no light. This usually means that the bulb socket is not making full contact with the thin metal tape that fits in the hole that the socket fits into. Sometimes it is corrosion on the metal tabs on the socket where they contact the thin metal from the board. Sometimes the thin metal from the board isn't stuck down the hole that the socket fits into. Sometimes there is a hairline crack on that thin metal tab and the contact point with the socket tabs is not through to the rest of the board.
    Thanks Bruce. In talking with Rick Jones I realized I had not retested the rotor after correcting the socket connection to the bulb. Once I tested the rotor again, the light came on so bad rotor. One is on it's way!
    Thanks to all for the input,
    Charlie
    Charlie P.
    1992 R100R

  11. #11

    Round 2

    Quote Originally Posted by 174713 View Post
    Thanks Bruce. In talking with Rick Jones I realized I had not retested the rotor after correcting the socket connection to the bulb. Once I tested the rotor again, the light came on so bad rotor. One is on it's way!
    Thanks to all for the input,
    Charlie
    OK, new rotor from Rick is now installed and his charging book is on backorder. So turned on the key and charging dashlight is now lit. Then went for a ride and the dashlight stayed on and got brighter as the revs increased. The voltmeter shows 14.3-14.4v just like it did before the rotor failed.

    I just went through Snowbums guide but couldnít find a ďlight staying on while having 14.xx voltsĒ. I swapped out the voltage regulator, same problem with light staying on.

    Any ideas to troubleshoot this?
    Thanks, Charlie
    Charlie P.
    1992 R100R

  12. #12
    Liaison 20774's Avatar
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    When you say voltmeter, what is that? Does the bike have a built-in voltmeter or are you measuring the voltage across the battery terminals? A built-in voltmeter is ball-parkish...it would be nice to know what is reading at the battery, say at 3500 RPM.

    For the gen light to be lit, that's an indication that the voltage on either side of the gen light is different. If the voltage is the same, then no current flows and the gen light is off. One side of the gen light basically reflects the battery voltage while the other side of the gen light is an indication of the output voltage of the alternator. Sounds like the alternator output is pretty high.

    To install the rotor, you had to remove the stator. Are you positive that the stator and connections are back correctly?
    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!

  13. #13
    Quote Originally Posted by 20774 View Post
    When you say voltmeter, what is that? Does the bike have a built-in voltmeter or are you measuring the voltage across the battery terminals? A built-in voltmeter is ball-parkish...it would be nice to know what is reading at the battery, say at 3500 RPM.

    For the gen light to be lit, that's an indication that the voltage on either side of the gen light is different. If the voltage is the same, then no current flows and the gen light is off. One side of the gen light basically reflects the battery voltage while the other side of the gen light is an indication of the output voltage of the alternator. Sounds like the alternator output is pretty high.

    To install the rotor, you had to remove the stator. Are you positive that the stator and connections are back correctly?
    Thanks for the feedback. The voltmeter is a digital ďBugĒ unit (no longer made but known for their reliability for use with motorcycles and snowmobiles) across the battery terminals. I confirmed this reading with v-ohm meter across the battery terminals. The voltage at 3500rpm is 14.1v.

    Good thought about the connections being the same, Iíll confirm that tomorrow. I also thought one of the brushes may need replaced as it is 1-2mm shorter than the other brush but I donít believe this should impact anything, only if there was no charging present.
    Thanks,
    Charlie
    Charlie P.
    1992 R100R

  14. #14
    Airmarshal-IL James.A's Avatar
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    In certain, odd circumstances, a single diode can fail but the system will still supply the electrical system but not charge the battery. I/we saw an example of this at Air Central at the national rally in Minnesota a few years back.

    A person might endeavor to learn how to test the diodes in the board individually.

    Depending on which diode in the board is failed, the V.O.M meter can show a positive result, but the output will be alternating current. That will not charge a battery. If you have a V.O.M. that indicates alternating current in the Direct Current mode, this can be ruled out. On some meters, this displays as a flashing L.E.D on the meter. I do not own a meter as sophisticated as that, but I have seen one or two of them in the kit of heavy equipment mechanics that I know.

    Another thing to consider is this, In my experience, the failed diode board allows the battery to fall down slowly depending on the rate of drain on the battery. If the diode board is supplying A.C., the bikes lights and ignition will still still still function but the battery slowly dis-charges. With a failed diode board on my /5, the red discharge light actually gets brighter as the battery voltage drops.

    Please do not buy a diode board based on my recommendation. I would be willing to send you a known, good spare to "fluke" it out. Send me a P.M. to explore this further.
    1973 R75/5

  15. #15
    Registered User ebeeby's Avatar
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    Quote Originally Posted by James.A View Post
    In certain, odd circumstances, a single diode can fail but the system will still supply the electrical system but not charge the battery. I/we saw an example of this at Air Central at the national rally in Minnesota a few years back.

    A person might endeavor to learn how to test the diodes in the board individually.

    Depending on which diode in the board is failed, the V.O.M meter can show a positive result, but the output will be alternating current. That will not charge a battery. If you have a V.O.M. that indicates alternating current in the Direct Current mode, this can be ruled out. On some meters, this displays as a flashing L.E.D on the meter. I do not own a meter as sophisticated as that, but I have seen one or two of them in the kit of heavy equipment mechanics that I know.

    Another thing to consider is this, In my experience, the failed diode board allows the battery to fall down slowly depending on the rate of drain on the battery. If the diode board is supplying A.C., the bikes lights and ignition will still still still function but the battery slowly dis-charges. With a failed diode board on my /5, the red discharge light actually gets brighter as the battery voltage drops.

    Please do not buy a diode board based on my recommendation. I would be willing to send you a known, good spare to "fluke" it out. Send me a P.M. to explore this further.
    I think you just nailed it....
    1973 R75/5

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