Alternator Life

[bizzaro]

My alternator at idle reads zero volt output, and my neutral light flickers.  Charging light remains off.   As soon as I rev to about 1.2k, the output is 13++volts, and the neutral light remains steady. I have just shy of 80k on the bike.  Is it time for a rebuild or replacement?  I would rather be proactive than stranded,  But prefer riding to wrenching!  And yes I did my search, and found nothing definitive on life expectancy of the alternator.  Frankenduck, in a post in another thread said, at idle it should be producing. 

Thanks,
Bizzaro 

[The Mighty Gryphon]

There are brushes that can wear out, and the regulators are known to go bad.  I had to replace the regulator on a '88 K100RS. 

My K75RT had to be at 2000rpm or above to have any alternator output.  Funny thing was that even though the battery wasn't charging the idiot light didn't come back on so I could be sitting there running the battery down without knowing it.

[bizzaro]

Hey MG, Good to hear from you!
My charging indicator light is off, as it should be.  The flickering is my neutral light.  I am wondering what the general life expectancy of the alternator is on the 94 K,(50 amp)  I modified my post to better reflect the symptoms.
Bizz

[Laitch]

As soon as I rev to about 12k, . . .

Give 'er hell, Biz!

[frankenduck]

Where are you reading zero?

Is the charge light in the cluster illuminated before you hit the start button?

[bizzaro]

Laitch,
Really..........................thats it?? You OK??   ( I added a decimal for ya. 1.2 K.  Such a stickler for details!)
 

Duck,
Yes, with the ignition on, the battery/charge indicator light is on.  With the bike running,  it goes out as it should.  My idle is pretty low, about 900 rpm.  But I don't get a reading from my alternator till I hit about 1200 rpm.
Bizz

[The Mighty Gryphon]

Hey, Bizz, good to see you are still kicking and not treading water up there with Laitch.

[bizzaro]

Well, Actually, my town got it bad. Lost our Market. For good this time I think. They cut a huge hole in the wall and were using bobcats to hoe it out to dumpsters and dump trucks etc.  Very sad.  Many businesses, homes a total wreck.  My house is fine!

[rbm]

A flickering neutral light at idle could be starter motor related.  Weird electrical faults and behaviours can be traced to starter brushes being too short or the starter dirty.  Have you serviced the starter in the time you've owned the bike?

[frankenduck]

A flickering neutral light at idle could be starter motor related.  Weird electrical faults and behaviours can be traced to starter brushes being too short or the starter dirty.  Have you serviced the starter in the time you've owned the bike?

Or a flaky gear switch on the trans.

[frankenduck]

Please answer my question: Where (at what electrical points of contact) are you measuring voltage?

Since we know that the bulb works and it goes out when the bike is running, the alternator is working. Here's how the charge indicator bulb works:

K75, K100, K1, K1100 Instrument Cluster Charge Lamp

OERATION:
1 – When the key is turned on it should be lit. (If not then it may be a burned out bulb or other issue.)
2 – When the bike is running it should go out to indicate that the alternator is working.

HOW IT WORKS:
The charge warning lamp has two terminals:
One terminal is 12V from the green/black power wire that powers the instrument cluster from Fuse 1.
The other terminal is connected to a blue wire from the alternator that monitors the output voltage of the alternator.

When the bike is turned on but not running the bulb has 12V at the power terminal and 0V from the alternator's blue wire. It therefore illuminates.

When the bike is running and the alternator is working there’s 12V at both of the bulb’s terminals so the net difference in voltage potential across the bulb is zero. It does not illuminate.

[bizzaro]

Robert.  Thanks for your suggestions.  I will try the in gear roll backwards brush clean up first.  The flickering light is not the issue for me.  The rpm (pun intended) late charging and battery health is my concern. IE: the draw on my battery.   The flickering neutral indicator appears to be clearly related to my low idle.  I will bump the idle up a bit.

Duck, I am taking the readings at both the Battery terminals, and the alternator.  And thanks for the explanation of the function of the charging indicator.  That light is working properly. 

[bizzaro]

My suspicion confirmed:
Bad Battery!! by

[Laitch]

  Here! Have some. It was only soaked in flood water for 50 hours.