I replaced the generator brushes and springs. There was nothing wrong with the old ones, which were rather new.
I watched the brushes on the rotor, with the motor running, and they were steady, no movement or bouncing. The rotor appears perfectly round, and is rarther new.
I repolarized the generator magnets and went for a ride. The generator only came on at very low idle, and went off as soon as the rpms were increased a little, which to me indicates a strong charging system.
However, I was again able to cause the old problem to occur. If I use the headlight, and let the rpms drop to idle so that the generator light comes on, then the generator light will stay on, and will flash or pulse as the rpms are increased.
I have replaced every component, and had the system checked by an expert, yet the generator continues to lose polarity on my command. So now I will install a switch so I can easily repolarize the generator from the saddle.
R27 generator light comes on with headlight
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Han Verhagen
Re: R27 generator light comes on with headlight
Allan,
I would only install a generator polarization switch temporarely. Just to make sure you are able to come back home after a ride.
As the aim of this forum is helping each other to improve the technical conditions of our BMW's and not to obscure their faults I think I should suggest you not to give up.
You have a fault in the electrical system of your R27 !
Depolarization of the stator of a DC generator can only occur if the current in its windings reverses its direction. I understand at the moment the revs go to idle with headlamp on the charge lamp lights up. This indicates the automate contacts opened as they should. At this very moment the field current reversed be it for a very short moment.
Look at the circuit diagram how this possibly can happen. The current flows normally from D+ to DF. At idle revs DF should have ground potential via the voltage regulation contacts. You can measure this with a voltmeter. While increasing revs this potential should be somewhere between 0V and 6V. At higher revs this potential should be close to 6V. At no moment should this potential be higher than D+ as it provokes a current reversal and hence a depolarization of the generator.
Other point to check :
Regulator resistor : something between 5 and 10 ohm. One side to ground. Other side to DF.
Poles of the stator : have a current of 1A flow from D+ to DF and check with a compass North, South, North South.
As you have exchaged all components of the electrical system I guess you have somewhere a cable fault.
Do not give up
Imagine the nice feeling once you found the error!
Han Verhagen
I would only install a generator polarization switch temporarely. Just to make sure you are able to come back home after a ride.
As the aim of this forum is helping each other to improve the technical conditions of our BMW's and not to obscure their faults I think I should suggest you not to give up.
You have a fault in the electrical system of your R27 !
Depolarization of the stator of a DC generator can only occur if the current in its windings reverses its direction. I understand at the moment the revs go to idle with headlamp on the charge lamp lights up. This indicates the automate contacts opened as they should. At this very moment the field current reversed be it for a very short moment.
Look at the circuit diagram how this possibly can happen. The current flows normally from D+ to DF. At idle revs DF should have ground potential via the voltage regulation contacts. You can measure this with a voltmeter. While increasing revs this potential should be somewhere between 0V and 6V. At higher revs this potential should be close to 6V. At no moment should this potential be higher than D+ as it provokes a current reversal and hence a depolarization of the generator.
Other point to check :
Regulator resistor : something between 5 and 10 ohm. One side to ground. Other side to DF.
Poles of the stator : have a current of 1A flow from D+ to DF and check with a compass North, South, North South.
As you have exchaged all components of the electrical system I guess you have somewhere a cable fault.
Do not give up
Imagine the nice feeling once you found the error!
Han Verhagen
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Allan Atherton
Re: R27 generator light comes on with headlight
You said:
" . . . Depolarization of the stator of a DC generator can only occur if the current in its windings reverses its direction. I understand at the moment the revs go to idle with headlamp on the charge lamp lights up . . . At this very moment the field current reversed . . . The current flows normally from D+ to DF. At higher revs this potential should be close to 6V. At no moment should this potential be higher than D+ as it provokes a current reversal and hence a depolarization of the generator . . . I guess you have somewhere a cable fault."
What fault in a cable could cause the potential at DF to be higher than at D+ and thereby cause depolarization?
Do you mean that a cable could be disconnected, or broken, or poorly grounded?
" . . . Depolarization of the stator of a DC generator can only occur if the current in its windings reverses its direction. I understand at the moment the revs go to idle with headlamp on the charge lamp lights up . . . At this very moment the field current reversed . . . The current flows normally from D+ to DF. At higher revs this potential should be close to 6V. At no moment should this potential be higher than D+ as it provokes a current reversal and hence a depolarization of the generator . . . I guess you have somewhere a cable fault."
What fault in a cable could cause the potential at DF to be higher than at D+ and thereby cause depolarization?
Do you mean that a cable could be disconnected, or broken, or poorly grounded?
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Han Verhagen
Re: R27 generator light comes on with headlight
Allan,
Perhaps "cabling fault" would have been a better phrasing. A component of the elecrical system is not branched to the other components as it should. You restaured the R27. An error is made while rebranching the wiring.
I own a R25/2 and a R50, not a R27. Hence I do not know how your cables run physically. URL :
http://www.beemergarage.com/documents/genadj.pdf
provides an excellent circuit diagram (not wiring diagram) + test instructions. Show this document to your expert and ask him to verify whether your electrical installation conforms this drawing. If your bike was in my garage I would first check whether the regulator resistor is well branched to ground on one side and to DF+ on the other side.
Regards
Han Verhagen
Perhaps "cabling fault" would have been a better phrasing. A component of the elecrical system is not branched to the other components as it should. You restaured the R27. An error is made while rebranching the wiring.
I own a R25/2 and a R50, not a R27. Hence I do not know how your cables run physically. URL :
http://www.beemergarage.com/documents/genadj.pdf
provides an excellent circuit diagram (not wiring diagram) + test instructions. Show this document to your expert and ask him to verify whether your electrical installation conforms this drawing. If your bike was in my garage I would first check whether the regulator resistor is well branched to ground on one side and to DF+ on the other side.
Regards
Han Verhagen
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Allan Atherton
Re: R27 generator light comes on with headlight
"..Show this document to your expert ..."
Thanks for all the information. I saved the PDF document for viewing, but it was locked so that it could not be printed or copied.
Thanks for all the information. I saved the PDF document for viewing, but it was locked so that it could not be printed or copied.
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Allan Atherton
Re: R27 generator light comes on with headlight
"...You restaured the R27. An error is made while rebranching the wiring. ..."
Actually, Guenther Wuest installed and connected the new wiring harness, and everything worked OK for a year and several thousand miles. Then the old pole housing burned and was replaced. After another year the rotor appeared to be bad so it was replaced. And and after another year the generator began losing polarity.
Actually, Guenther Wuest installed and connected the new wiring harness, and everything worked OK for a year and several thousand miles. Then the old pole housing burned and was replaced. After another year the rotor appeared to be bad so it was replaced. And and after another year the generator began losing polarity.