MOTOBRICK.COM

TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => The Motobrick Workshop => Topic started by: bizzaro on July 19, 2023, 04:15:04 PM

Title: Alternator Life
Post by: bizzaro on July 19, 2023, 04:15:04 PM
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 
Title: Re: Alternator Life
Post by: The Mighty Gryphon on July 19, 2023, 04:26:28 PM
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.

Title: Re: Alternator Life
Post by: bizzaro on July 19, 2023, 04:33:12 PM
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
Title: Re: Alternator Life
Post by: Laitch on July 19, 2023, 04:36:18 PM
As soon as I rev to about 12k, . . .
Give 'er hell, Biz! :laughing4-giggles:
Title: Re: Alternator Life
Post by: frankenduck on July 19, 2023, 04:39:46 PM
Where are you reading zero?

Is the charge light in the cluster illuminated before you hit the start button?
Title: Re: Alternator Life
Post by: bizzaro on July 19, 2023, 04:48:57 PM
Laitch,
Really..........................thats it?? You OK?? :laughing4-giggles:  ( I added a decimal for ya. 1.2 K.  Such a stickler for details!) 112350
 

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
Title: Re: Alternator Life
Post by: The Mighty Gryphon on July 19, 2023, 04:55:31 PM
Hey, Bizz, good to see you are still kicking and not treading water up there with Laitch.
Title: Re: Alternator Life
Post by: bizzaro on July 19, 2023, 05:03:06 PM
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!
Title: Re: Alternator Life
Post by: rbm on July 19, 2023, 08:07:42 PM
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?
Title: Re: Alternator Life
Post by: frankenduck on July 19, 2023, 10:53:47 PM
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.
Title: Re: Alternator Life
Post by: frankenduck on July 19, 2023, 11:01:26 PM
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.
Title: Re: Alternator Life
Post by: bizzaro on July 20, 2023, 08:32:40 AM
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. 
Title: Re: Alternator Life
Post by: bizzaro on August 03, 2023, 10:04:09 AM
My suspicion confirmed:
Bad Battery!! icon_cheers by
Title: Re: Alternator Life
Post by: Laitch on August 03, 2023, 11:06:04 AM
 112350 Here! Have some. It was only soaked in flood water for 50 hours.  :smoke07