How do you check if the alternator is functioning properly.

Discussion in 'Parallel Universe' started by EnderTheX, May 8, 2011.

  1. EnderTheX

    EnderTheX Dirt Rider

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    Hey yall, I thought I would start a new thread specific to this topic.

    Can someone explain how to check if the alternator is working? Is there somewhere to hook up directly to the alternator wires and get a reading? Can you do it solely from the battery leads?

    If someone can explain it to me I can go do it and post up some detailed pictures :D

    Thanks!
    #1
  2. ebrabaek

    ebrabaek Long timer

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    I have not worked on this stator before..... But they operate the same. As Finn said.... open circuit is bad...... heat or something else have broken the circuit...or so. There are 3 primary wires coming from the stator.....yielding ac voltage. Try to set the meter to ac.... and you should have 40-80 volts ac....between each of the three phase. Ie ...Y1...Y2....Y3 ...first between y1 and y2......then y2 and y3....then y3 and y1.... that should be done around 3000 rpm......but in many instances will yield same results at idle...unless there is a big draw on the circuit. If any of those three legs don`t yield ac....stator is toast..... Then it`s on to the RR..... Easiest way..... measure the battery volt...before engine start...... then start the motor.... should jump to about 14,6 volts...minimum.
    Post the results........ Boy Dallas is hot and muggy...... Just got home from an overnighter....For the TCU grads.....:thumb:thumb

    Erling

    Edit: Just wan`t to clarify the procedure Finn posted above..... Use same 3 leads.....as measuring the ac voltage.... Bike off..... and plug disconnected...... any open measurement..... is bad..... like y1 and y2..... then y2 and y3....etc. Those should be about 0.5 ohms... If they are open....that means that circuit is bad. The take each of the legs and measure to ground.....No continuity is good....ie... you want an open circuit here... If you don`t ...that means that part of that coil is short circuited to ground.

    edit2: for clarification...
    #2
  3. cathulu

    cathulu Been here awhile

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    Just to correct, 0 ohms is a short circuit. An open circut will be "infinte" ohms - at least in the hundreds of megohms anyways...
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  4. ebrabaek

    ebrabaek Long timer

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    Your right..... I could have written that a bit better.....:D
    :thumb:thumb

    Erling
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  5. EnderTheX

    EnderTheX Dirt Rider

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    OK... After relieving some stress by changing some tires and downing a few rum and cokes, I get to checking the alternator. My battery is still charging three hours later (on the junior tender)... totally screwed.

    Here is a quick summary with pictures to back it up in case my method is off...

    If you look at the connector (picture 2) I call the left wire "1", middle "2" and right "3".

    Resistance between the wires, 1-2, 1-3, 2-3 all come to about 0.2 or 0.3 ohms.

    When the bike is running at 3k RPM here are the values for AC voltage:

    1-2: 8.7V :eek1
    1-3: 1.9V :cry
    2-3: 12.4V :huh

    At idle the voltages were about 10% lower.

    Could someone please duplicate this on their functional bike as a control? I would like to compare values... :D


    So this is where I access the plug:

    [​IMG]



    I think this is the plug circled in red:

    [​IMG]



    I can get my probes in contact without disconnecting the plug like this:

    [​IMG]



    Here is the typical resistance measurement when the bike is off:

    [​IMG]




    This is how I measured the AC voltage, this is 1-2... (1-3 was 1.9V, 2-3 was 12.4V).

    [​IMG]


    :becca
    #5
  6. JoelWisman

    JoelWisman Long timer

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    That looks like the plug to me. The AC voltage readings are consistant with a shorted stator. The resistance readings don't say much, but consumer multimeters aren't going to say much regarding resistance unless in very experienced hands.

    If your in warranty, I'd take it to a dealer.

    If your not in warranty, remove the stator and bring it into an alternator or motor shop for baking or rewinding.

    The stator is easy to remove, if memory serves, all you need is 8 and 10mm sockets and a torque wrench acurate at low values.

    The stator is bolted to the inside of the left engine cover, so you will need that gasket. Worse case, the stator rewind and gasket SHOULD cost around $100.00

    Good luck

    P.S. Your black test lead is in the wrong hole. It probably won't make any difference as long as your multi meter does not use a solid state shunt and your fuse is good, but for reference, the black lead goes in the "com" terminal for all but amperage readings.
    #6
  7. EnderTheX

    EnderTheX Dirt Rider

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    Cool... thanks for the info. I really hope I am still in warranty!!! If I am not I am certainly going to try the re-wind route, no sense spending a ton of money if not needed...

    Did I mention I suck at electrical issue and this is a brand new multimeter? :rofl Thanks for the tip, I hope the readings are still good... :lol3
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  8. ebrabaek

    ebrabaek Long timer

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    As Joel said.....Bad stator........ I would like to echo what Joel said about the black lead...... Just to be safe.... The tests should be run with it in the com. ( ground) plug on the meter...... I`m not familiar with the Craftsman.....But Mine will not measure ac volts with the black in the amp receptacle..... If that is in fact true readings... your stator is toast....... Sorry. I guess I was wrong earlier......:thumb:thumb

    Erling
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  9. The Griz

    The Griz Long timer

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    Another way to check if the alternator is working properly is to simply touch the + and - pins of the tester to the + and - terminals of the battery while the bike is running. Multimeter should be set to DC voltage with the decimal point positioned as so: 00.0. It should read a constant of around 14+v when the bike is running, and drop back down to around 10-12v when the bike is off. The reason the voltage is greater when the bike is running is due to the fact that the alternator is spinning and charging the battery. If the voltage does not read above 12v when the bike is running, then the alternator/charging system is not working.
    #9
  10. EnderTheX

    EnderTheX Dirt Rider

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    Yep... at 4k RPM my battery terminals read a whopping 12.7V

    Now I just hope I can make it to the dealer without dying on the side of the highway, I think I can if I charge the battery all the way up, 40 minute ride... I think the bike is mostly running off battery power because it drains it so fast.
    #10
  11. JoelWisman

    JoelWisman Long timer

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    This is true from a general sense, though I would use different figures.

    Under modest load, a fully charged and healthy AGM battery will rest at 12.8v at 68 degrees F. If the temperature is lower, the resting voltage will be lower and visa-versa. The coefficient for resting voltage change is usually less then .01 volts per degree F but can be relevant if it is very cold or hot. Also different brands of AGM battery can have slightly different chemistry that changes battery resting voltage .1 volts or so, to say nothing of different styles of lead acid batteries such as gel or flooded. Lastly some batteries for motorcycle use are no longer even lead acid based.

    In general, above 12.8 volts while the bike is idling means the charging system is producing something, but the reverse is not as conclusive and this still does not mean the charging system is working as it should.

    If a battery is healthy but heavily discharged, readings at the battery below 12.8 volts DO NOT mean the charging system is not working perfectly. A heavily discharged battery will absorb all current from a working charging system for some time before every getting above 12.8 volts.

    Another possibility is the load is excessive and preventing the charging system from keeping up and exceeding 12.8 volts. A common cause of this is too many accessories attached to motorcycle and switched on. Another possible cause is a battery with a shorted cell.

    Once again, a voltage above 12.8 when the bike is idling, preferably above 13.2 volts, is a very good sign. Being below 12.8 volts while idling is not conclusive that there is a defect or failure.


    to conclusively find charging, starting and load failures quickly, I need a current shunt or inductive DC current pickup. AC voltage readings and very accurate DC voltage readings, and a megger.

    To conclusively test the PM alternator in our bikes...
    First test the AC voltage from pin to pin at the alternator plug just like Ender did. With the rectifier / voltage regulator unhooked you should be seeing 18+ volts at each of the alternator pins (assuming your meter is good and it's hooked up right :) if you do not, your alternator is BAD.

    Next, test current output of each leg of the 3 phase alternator. This is done with a carbon pile and some specifications I do not have, but could extrapolate from a properly working same bike. If the current is too low, the alternator is BAD.

    Finally check the stator insulation resistance with a megger. High resistance good, low BAD.

    Only once an alternator passes all the above tests can it be said to be good with confidence. A failure of any of the above tests means its BAD.

    Passing all of these tests does not mean your charging system is working as there are other components in the system as well.


    I haven't personally seen any stator failures on the F800GS, but I have heard about more then I would like to and some of my customers are concerned.

    Hopefully you are under warranty EnderTheX, but if you are not, PM or call me and I will help find a motor or alternator shop that can bake or rewind it. The cost of the entire alternator is disconcerting, but the stator is the only part I expect to ever see failures on and should be possible to make better then new for little cost and effort. I have a vested interest in making this problem minor :)
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  12. EnderTheX

    EnderTheX Dirt Rider

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    Thanks, I may try that since I will be riding in the daytime to the dealer and I know it is easy to unplug the lamp. I may also ask you for contact info for your rep if something happens.




    I am pretty sure I am still in the three year window for warranty since my bike was originally purchased beginning of 09 so it should be good until beginning of next year... 2012 (right...?).

    I've run into a string of bad luck recently (separate from my bike too) so I wouldn't be surprised if I am asking for a place that can rework the stator. I certainly appreciate help with sourcing a repair shop since my quick research online for a local shop didn't show anything promising.


    I will also run the test again when I get home to see if putting the lead in the right spot has the same results :lol3
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  13. The Griz

    The Griz Long timer

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    Good stuff here Joel.

    However, the exact resting DC voltage of a 12v DC battery will change depending on battery manufacturer, battery design, and battery type (lithium ion, lithium polymer, or lead acid). This is why I used a broader voltage scope.
    #13
  14. JoelWisman

    JoelWisman Long timer

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    The resting voltage does change, but not that much for lead acid chemistry at reasonable temperatures. A quick check of my factory battery (the good grey one) is with it fully charged, idling with the alternator disconnected is 12.6 volts. As a quick check, I want to see something well above 12 volts when idling to assume everything is peachy.

    On a fully charged battery, anything below 13.4 volts at idle is cause for concern that at the least, load is heavy or battery is discharged. This is true at all temperatures and with all chemistry of batteries compatible with our charging systems.

    I doubt voltage will fall below 12 on a good fully charged battery till at least a half hour after the charging system has failed.
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  15. EnderTheX

    EnderTheX Dirt Rider

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    Hey check this out:

    http://www.electrosport.com/street-bikes/bmw/f650gs/stator-3-phase-102.html

    This looks like a brand new part to replace the OEM stator. It is only $125!

    I would assume the F650GS stator is the same as the F800GS?

    I also found this site: https://www.rmstator.com/en/motorcycles/bmw/1-bmw_motorcycle_stator_repair_all/all_categories.htm

    It looks like they repair stators...

    So the brand new stator that is after market is $125 and to repair a stator it is $150... hmmm... Do you think there is anything special about the OEM stator compared to a replacement?
    #15
  16. JoelWisman

    JoelWisman Long timer

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    It looks to me that the F650GS they are talking about on the first site is the older single. They also list one for the F800ST and my parts guide says that SHOULD be the same part.

    Theres nothing special about the OEM stator, other then on at least some of the older bikes, the insulation is not that good.

    Everything advertised for motorcycles is always more expensive. Sans warranty, i'd look for a shop that rebuilds in house.

    It is laughable how easy it is to make a stator. 1: put a new nomex or fiberglass sleeve on each pole piece. 2: get varnished or glassed wire of appropriate size (14 gauge perhaps? easy to tell once your looking at it), wind it around each pole piece with the same number of turns as original and follow the pattern of the original. 3: Protect the terminations with glass tape.
    4: dip the completed assembly in varnish or glass (glass is better). Bake it at the temperature the varnish or glass manufacture recommends. DONE

    If you want serious reliability meg / hot test, dip it again and bake it again if your really hard core. DONE

    The style of stator on the F800GS is the easiest to rewind in the world. If I had facilities like I did when I was an industrial electrician, it would take me 10 bucks in supplies and 15 minutes of labor to rewind it and use far higher temperature insulation then BMW did.

    You should still be well within warranty Ender, but if you weren't, I would find someone that still practices the dying art of repair, rather then replacement.
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  17. cathulu

    cathulu Been here awhile

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    If you choose the rebuild route, why not see about throwing in some more windings for more current output...
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  18. EnderTheX

    EnderTheX Dirt Rider

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    Certainly! Joel puts forth a good case for a rebuild... especially when you think about the options for higher quality.

    Can someone explain to me how more windings would help? I understand thicker wire, better insulation and stuff like that but the geometry of the stator is a mystery. :D
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  19. JoelWisman

    JoelWisman Long timer

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    I would be cautious about thicker windings or more turns. There is room to add, but this is a PM alternator with a PM voltage regulator. PM regulators work by sinking excess capacity to ground.

    The voltage regulator on the f800 is that thing on the left side with all the fins to get rid of heat. It already gets hot enough to toast bread, increase the alternator capacity and your voltage regulator may melt down.

    It is certainly possible to increase capacity of the charging system, but for safety sake, the voltage regulator and wiring between alternator and battery would need to be upgraded too.

    Beyond any doubt though, you could greatly increase the robustness of the stator insulation, which would seem to be what is lacking on at least some of the stock stators.

    P.S. I am told BMW intends to eventually start selling the stator alone rather then only the whole alternator. This at least should reduce the cost of the failing part.
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  20. JoelWisman

    JoelWisman Long timer

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    This is a picture of the stator. it's bolted to the inside of the left engine cover.

    <a href="http://www.flickr.com/photos/joel_wisman/5354047067/" title="P1020938 by joel.wisman, on Flickr"><img src="http://farm6.static.flickr.com/5043/5354047067_a3828d3e4f_z.jpg" width="640" height="480" alt="P1020938"></a>
    #20