Alternator question...

[fbenach]

Hello guys, how´s life?
Have another question, regarding alternator, I think...

In the past days, I noticed my GEN light slightly coming on, from time to time...
Today, after a 100mile ride, I completely lost my turn signals, horn and pretty much the head and tail lights... also, my tach started to jump like crazy... even at low RPMs, it jumped to 7000 without actually having them...

I realize there´s a problem (dough!!) on generation, although my bike had the normal power it usually has...

My question is, how do I know if it is the rotor, the stator or everything at the same time? Diode board?

My mechanic will be seeing the bike tomorrow, and fix it hopefully, but I want to understand a little bit more on how this whole thing works!!

Also, an old friend, that has older bikes (Zundapp 55, Konsul 53) suggested me to go "electronic" on my bike... is that possible? a way of eliminating the alternator function and make it work some other way?

Thank you all, as always!!!
Take care

[Bob_Roller]

If the GEN light is coming on, most likely the rotor is not at fault .

Without testing each component, you don't know where the problem is .

[montmil]

You have presented us with multiple issues but little input into your efforts to troubleshoot the problems. Without knowing the age and condition of your battery, your confirmation of checking all grounding points and any tests run on the charging system... we're just tossing out ideas that could be way off. So...

Step One: Make a couple sandwiches and a glass of cool water.

Step Two: Read Snowbums lengthy treatise on the care and feeding of the Airhead charging system. Follow those instructions to the letter.

http://bmwmotorcycletech.info/trbleshootALT.htm

Plan to be on your compuKer for awhile. So many possibilities but, as most often, the issue will turn out to be something simple.

Suggest you try the troubleshooting techniques offered prior to leaving your Airhead with a mechanic and his healthy shop rates for diagnosing problems. $$$ He will likely be reading the same website as you.

For a classic example of how simple issues can generate complex and oft times expensive non-results, go to the Chit-Chat section and read this: http://forum.boxerworks.com/viewtopic.php?f=1&t=4914

[Luca]

Without testing each component, you don't know where the problem is .

Ditto

It would also be wise to check all of your electrical connections and make sure they are clean and tight

[Barry]

My question is, how do I know if it is the rotor, the stator or everything at the same time? Diode board?

There are lots of resources on the Internet about understanding and testing airhead charging systems but they are all too wordy to repeat here. If you search for "airhead charging system" you'll find them.

To give you some pointers:-

If the rotor goes permanently open circuit the charge light wouldn't come on with the engine stopped so it isn't that although the rotor can go open circuit intermittently due to centrifugal forces when running.

Brushes are a more likely and cheaper cause of your problems. Easy to check for excessive wear although I doubt you'll find a definitive measurement for minimum brush length. The bottom line is they must make good contact with the slip rings.

For testing the diode board I quite like this:-

http://www.frankhams.freeserve.co.uk/testing_the_diode_board.htm

[tvrla]

As mentioned already, if the light is coming on, it's probably not the rotor. The brushes are making contact as evidenced by the light coming on - the light is grounded through them, through the rotor to ground.

I've had problems with old brushes deteriorating and leaving a black, non-conductive coating on the alternator rotor slip rings that prevented the generation of electricity. Soon as that was cleaned up, all was fine again.

These alternators aren't the easiest things to understand. I'm pretty good with electricity and been doing this for years (got my first beemer over 20 years ago) and I still don't feel like I'm any kind of expert. That said, now's the best time to start learning these things, even though someone else is fixing it for you.

[fbenach]

Thank you all,
The article that Montmil included on his comment is very complete on the subject...
Still, as wirespokes said, it´s kinda confusing the way these things work.

On the other hand, I started the bike this morning rolling down the hill and went to the mechanic... we realized the light goes off around 4000 RPM and start to feed the  lights normally...
He´s gonna check the brushes and the diode board... we´ll see in a couple of days...

Again, you guys are the coolest... everytime I open this forum I learn a little bit more from you, and for that, I´m thankful!!

take care!!