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K100-forum.com » Technical, repair and troubleshooting » Electrical » Alternator low charge rate

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1Back to top Go down   Alternator low charge rate Empty Alternator low charge rate Tue Oct 06, 2020 7:42 pm

Rockman

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This just a question out of interest (as I have changed alternators).

I have a K100/75 33A alternator that wasnt charging below about 3000 rpm, and then only about 13 volts. I checked the brushes and they are well within specs. Any suggestions of the problem? Regulator??

I suppose all I am wanting to know is if it is a simple fix, or do I just bin it.

    

2Back to top Go down   Alternator low charge rate Empty Re: Alternator low charge rate Tue Oct 06, 2020 10:26 pm

robmack

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Is the bike stock or have you modified the thing, especially by replacing the charge bulb with a LED?


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3Back to top Go down   Alternator low charge rate Empty Re: Alternator low charge rate Tue Oct 06, 2020 10:55 pm

Rick G

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If the alternator light is working then I would suspect that the regulator is crook. They aren't specific to BMW so any good auto electrician will be able to get one. I recall hearing that some of the later VW beetles had the same regulator or if you are over this way I have some here you could try.


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4Back to top Go down   Alternator low charge rate Empty Re: Alternator low charge rate Wed Oct 07, 2020 1:21 am

Rockman

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RicK G wrote:If the alternator light is working then I would suspect that the regulator is crook. They aren't specific to BMW so any good auto electrician will be able to get one. I recall hearing that some of the later VW beetles had the same regulator or if you are over this way I have some here you could try.

Thanks Rick. I'm only looking to put it on the spares shelf so next time I am up your way I'll drop in. Do you know how to test the regulator off the bike?

    

5Back to top Go down   Alternator low charge rate Empty Re: Alternator low charge rate Wed Oct 07, 2020 3:37 am

tinyspuds

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I was amazed at the performance of my new regulator on a 50amp. 14.4v at anything above tickover. Well worth the $$


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1985 BMW K100RT + Hedingham HUB and LL’s. VIN 0028106.
1986 K100RS in boxes. VIN 0141918.
1954 Royal Enfield 350 Bullet. Original.
2000 Hayabusa with Charnwood chair, Wasp forks and EZS wheels.
    

6Back to top Go down   Alternator low charge rate Empty Re: Alternator low charge rate Wed Oct 07, 2020 4:49 am

Arlina

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The regulator is on it's end, replace for new.


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Alternator low charge rate Eu-log10  K1100RS/LT - R1200RT - R1100RS - Cagiva SST 350 Ala Verde - K75LT project - K75 Schurgers - K75S - K1100RS - K75RT - K75C
    

7Back to top Go down   Alternator low charge rate Empty Re: Alternator low charge rate Thu Oct 08, 2020 7:04 am

Dai

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Yep; sounds like the reg is dead. Or dying.


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8Back to top Go down   Alternator low charge rate Empty Re: Alternator low charge rate Thu Oct 08, 2020 9:17 am

Point-Seven-five

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I have the same problem on my K100RS SE, no output below 2500rpm. Replacing the regulator as part of the end of year maintenance.

No need to spend big bucks at the stealer. Got mine on eBay.


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Past:
1994 K75RT "Ilsa, She Wolf of the SS"
1988 K100RS SE "Special Ed"
1994 K75S "Cheetos"
1992 K100RS "Moby Brick" R.I.P.
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
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9Back to top Go down   Alternator low charge rate Empty Re: Alternator low charge rate Thu Oct 08, 2020 8:42 pm

Rockman

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Point-Seven-five wrote:I have the same problem on my K100RS SE, no output below 2500rpm.  Replacing the regulator as part of the end of year maintenance.  

No need to spend big bucks at the stealer.  Got mine on eBay.  
Do you have a link?

    

10Back to top Go down   Alternator low charge rate Empty Re: Alternator low charge rate Fri Oct 09, 2020 12:47 am

Point-Seven-five

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https://www.ebay.com/itm/Internal-Voltage-Regulator-BMW-K-12-31-1-459-286-BOALT-REG286/372744802792?fits=Model%3AK100%7CMake%3ABMW&hash=item56c95251e8:g:2VkAAOSw0Btb6OU4

I just put "BMW K100 voltage regulator" in the ebay search engine. You can also do the same search for K75 since they both have the same alternator.


__________________________________________________
Present: 1991 K100RS "Moby Brick Too"
 
Past:
1994 K75RT "Ilsa, She Wolf of the SS"
1988 K100RS SE "Special Ed"
1994 K75S "Cheetos"
1992 K100RS "Moby Brick" R.I.P.
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

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