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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, 18:42

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, 21:26

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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1987 K75 @k75retro.blogspot.ca
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3Back to top Go down   Alternator low charge rate Empty Re: Alternator low charge rate Tue Oct 06 2020, 21:55

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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"Man sacrifices his health in order to make money.
Then he sacrifices money to recuperate his health.
And then he is so anxious about the future that he does not enjoy the present; the result being that he does not live in the present or the future; he lives as if he is never going to die, and then dies having never really lived."   Dalai Lama


Bikes 1998 K1100 LT, 1993 K75 RT, 1996 K75RT, 1986 K75 GS, 1979 Z1300 Kawasaki
    

4Back to top Go down   Alternator low charge rate Empty Re: Alternator low charge rate Wed Oct 07 2020, 00:21

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, 02:37

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 $$


__________________________________________________
1985 BMW K100RT + Hedingham HUB and LL’s. VIN 0028106. (Not blind to the irony of an April 1 production date).
1986 K100RS in boxes. VIN 0141918.
1954 Royal Enfield 350 Bullet. Original.
    

6Back to top Go down   Alternator low charge rate Empty Re: Alternator low charge rate Wed Oct 07 2020, 03:49

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 (RIP) - Cagiva SST 350 Ala Verde - K75LT project - K75 Schurgers - K75S
    

7Back to top Go down   Alternator low charge rate Empty Re: Alternator low charge rate Thu Oct 08 2020, 06:04

Dai

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


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1983 K100 upgraded to K100RS spec, 1987 K100RT
Others...
1978 Moto Guzzi 850-T3, 1979 Moto Guzzi 850-T3 California,1993 Moto Guzzi 1100ie California
2020 Royal Enfield Bullet 500
    

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

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.


__________________________________________________
Present:
1994 K75RT
1991 K100RS
1988 K100RS SE

Past:
1994 BMW K75S
1992 BMW K100RS
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

9Back to top Go down   Alternator low charge rate Empty Re: Alternator low charge rate Thu Oct 08 2020, 19:42

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 Thu Oct 08 2020, 23:47

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:
1994 K75RT
1991 K100RS
1988 K100RS SE

Past:
1994 BMW K75S
1992 BMW K100RS
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

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