How do you check if the alternator is functioning properly.

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

  1. yns

    yns cretan inside

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    In fact, all the measurements are made with the R/R disconnected. I have not changed anything to the electrical system apart from an extra 12V socket (directly on the battery) for charging the cell phone with the engine off. But I did this last summer... Seems that I have to go to an electrician to have the bike checked but first I will try to have a measurement done at the terminals with the socket disconnected (and the r/r plug connected) to exclude that this is that shorts out.

    Edit: it wasn't the extra socket... And my neighbors didn't like the fact that I was testing with engine at 4.000 rpm at 10:00 pm... :D
  2. ebrabaek

    ebrabaek Long timer

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    Ha ha... I understand..... In my home country of Denmark, they would not look at this kindly either. You really dont need the electrician. Just do the three measurements, as in my thread. It is a series of tests. If any one fails, your stator is bad. Ie. You cannot have two tests be ok, and a third bad..... Then the stator is bad.
  3. itsatdm

    itsatdm Long timer

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    I think I have a dying but not quite dead stator. A resting battery charge of 12.6. It will slowly get up past 13v, but only if the engine revved past 4,000 rpm. Below 12v with high beam and heated grips on high with the engine running.

    The bike will fire up even with a battery voltage less than 12v :huh

    Here are the stator readings:

    Resistance is .5 across the board.

    At idle I am getting 28 volts on all 3 prongs

    At 3,000 rpm 1-2 is 28
    1-3 is 40
    2-3 is 52v

    Sorry the computer seems to want to put my values where it wants. I have done a test 2 and 3 with a warm engine and at idle the voltage drops for all 3 connections from 15 to 24v. At 3,500rpm 1-2 remains 15v and the others range from 47 to 59v

    prongs to ground are all 0.00

    Before I order up, is there something else I should be looking at?
  4. JRWooden

    JRWooden Long timer

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    Those numbers seem a bit screwy to me ... but not good....

    If you have ZERO resistance to ground that's a killer ...
    There should be "infinite" resistance from any of the three prongs to ground so ... if it's really zero I would say ... yeah you are screwed
  5. itsatdm

    itsatdm Long timer

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    Looks screwy to me too, that why I posted. With 2 test with a hot engine. 1-2 stayed at 15v no matter the revs. 1-3 started at 18v at idle, then 47 on the first hot test and 24v on the second at 3,500rpm. 2-3 is now 24v at idle then 54 and 58v at 3,500rpm.

    I don't know if it is normal for the voltage to change, but the same thing happened when taking readings at the battery. Different day, different charge rate, none of it good.
  6. ebrabaek

    ebrabaek Long timer

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    As Woody mentioned by having zero ohm to chassis, means a shorted stator. When you measured the ac.... you had the r&r disconnected...yes.... If yes, then your output is too low. My vote is bad stator.
  7. ebrabaek

    ebrabaek Long timer

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    Could be the short is somewhat varying with the vibrations....who knows.
  8. JRWooden

    JRWooden Long timer

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    Yeah, what he said...

    If you did NOT have stator disconnected I'm not sure what readings "should" look like ....

    R/R could be clouding the picture ....

    but with stator disconnected there should absolutely be very high / infinite resistance to ground from all three pins on the stator harness.

    So if you are showing "zero" or close hot or cold that's "end of life" for stator.... unless the harness has shorted to ground somewhere along the line....
  9. itsatdm

    itsatdm Long timer

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    I feel like an idiot. Yes the RR has been disconnected. I have some real numbers that I can trust. First it is not shorted. The bolt I was grounding on was encapsulated. The readings are .4, .4, and .5

    Idle Voltage is 15v, 20v, 25v. At 3,000rpm they are 28v, 43v, 55v the highest readings I can get are 30v, 55v and 68v.

    Obviously I have a phase going south that allows the bike to charge the battery, but hi beams and max grip heat are questionable.

    I may be able to nurse this stator along for a while, but I am going to replace it while still in the comfort of my garage.

    How do you convert the voltage numbers to total wattage?
  10. ebrabaek

    ebrabaek Long timer

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    You simply multiply the volts with the amperage draw. But you have to know two of the three. You can measure the amperage draw by putting your meter in line with the item. Like break the circuit on the positive, and insert your meter. What you then read, multiply it with the voltage, and you have watts.
  11. JRWooden

    JRWooden Long timer

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    Gary:
    It looks like perhaps you have two phases headed south,
    one is just closer to being there ....

    In practical terms if you are going to nurse it I think you can just monitor voltage while riding and so long as you don't get much below 13V you should be OK but likely stator will continue to get worse so you'd want to have a "Plan B" ... for getting back home if you are far away...

    I've seen both Rick's and ElectroSport's stators on eBay at pretty good prices .... personally I'd go with the ElectroSport...
  12. itsatdm

    itsatdm Long timer

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    Plan B is in effect. Electro sport has been ordered. I have lousy phone service where I live. I would rather change it now.
  13. JRWooden

    JRWooden Long timer

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    good plan .... that's what I'd do :clap
  14. Full Power

    Full Power Long timer

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    Easy: Watts = Volts x Amps
    You are measuring 'open-circuit' voltage, ie No-Load.
    zero amps ( multiplied by ) open-circuit voltage (equals ) ZERO watts.
  15. itsatdm

    itsatdm Long timer

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    It was a theoretical question. Stator is capable of 400 watts, which should be 28 amps? Bike uses around 200 watts to run and keep the lights on. Curious to see what the wattage my dying stator can produce based on the AC voltage numbers I have at 3,000rpm, if the bike was using 200 of them.

    I am coming up with 249 watts at 3,000 rpm and 292 at max. Math is hard for me, obviously what ever it is, it is not quite enough.
  16. Bayner

    Bayner Long timer

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    That's the way mine went south.
    I limped it back into BC from central Oregon by unplugging the headlights and shutting down everything I could that used power. Once I had done that I could even use the starter rather than having to push start it...
  17. itsatdm

    itsatdm Long timer

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    Ordered my stator Tues, got it Thurs. and installed it this AM:thumb. Electro Sport doesn't fool around with delivery. All OK now.

    Picked a gasket up at the dealer, making sure they knew it was for the stator side. I was told this is the first F800gs stator that they have ever heard of needing replacement.

    You guys need to quit blowing this out of proportion.:rofl
  18. ebrabaek

    ebrabaek Long timer

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    :lol3:lol3:lol3:lol3:lol3:lol3:lol3:lol3:lol3
  19. JoelWisman

    JoelWisman Long timer

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    Then your bike must be the only one they ever serviced. I replaced 3 K7x staters in the same week the last week I was with BMW.
  20. itsatdm

    itsatdm Long timer

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    It is probably just me. I had the first cracked fuel tank the dealer had ever seen too. The 2nd one was the new bike on his show room floor.:lol3