BMW K bikes (Bricks)

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roach374

roach374
Silver member
Silver member
So I know that the charge indicator light (or some equivalent resistance) is *not optional* in the alternator / charging circuit, and I've read in various places that I can replace it with a 100Ohm, 5W resistor, but I wanted to triple check my new wiring. Can I just plug the alternator straight to battery on the positive side, and Ground on the negative (through the resistor)?


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1993 K75 standard
    

robmack

robmack
Life time member
Life time member
No, that's not correct. You connect positive of the alternator to the positive of the battery, the negative goes frame ground, and the Blue wire for the field winding goes through a resistor (that substitutes for the charge indicator) to a switched power source.


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Robert
1987 K75 @k75retro.blogspot.ca
http://k75retro.blogspot.ca/
    

Two Wheels Better

Two Wheels Better
Moderator
Moderator
@roach374 wrote:So I know that the charge indicator light (or some equivalent resistance) is *not optional* in the alternator / charging circuit, and I've read in various places that I can replace it with a 100Ohm, 5W resistor, but I wanted to triple check my new wiring. Can I just plug the alternator straight to battery on the positive side, and Ground on the negative (through the resistor)?
As an alternative reality viewpoint, my Big Block has a 50amp K alternator, but zero instrumentation bar my Android phone, with an app for a speedometre, and it charges como Dios manda (as God intended), no charge indicator light at all. 

Perhaps Deus ex machina after all.


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1970 R60/5, OZ '77 R75/7-R100, '85 K100'87 K75C, OZ '87 K100RS, '93 K11-K12 Big Block, '93 K1100RS, '95 R100-Mystic, '96 K1100RS, '98 K1200RS, '00 K1200RS, '02 K1200RS, '03 K1200GT, '04 R1150R'04 R1150RT, '05 K1200S, '06 K1200R, '07 K1200R, '09 K1300GT & 2013 R1200RT-P  - Beemers owned still or sold.

~We all believe what we want to believe in - Rob Dickinson
    

roach374

roach374
Silver member
Silver member
@robmack wrote:No, that's not correct.  You connect positive of the alternator to the positive of the battery, the negative goes frame ground, and the Blue wire for the field winding goes through a resistor (that substitutes for the charge indicator) to a switched power source.

Thanks Rob. There are only two wires coming out of my alternator. Is it grounding to the frame?

I'm having trouble reading the wiring diagram. What is the "switched power source" in this case? 

Thanks again for your help.


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1993 K75 standard
    

Dai

Dai
Life time member
Life time member
Alternator case grounds through the engine. The nearest 'switched power source' (i.e. a wire that gets power when the ignition switch is turned on) is the all-green wire on the load shed relay.


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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
    

Laitch

Laitch
Life time member
Life time member
It looks like a couple of posters here disdain harboring any device that might indicate battery or charging condition. Clearly, they're rejecting idiocy. Are they haruspical or prescient?


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1995 K75 81,000 miles
['93 K75] Battery charging circuit resistor? Usa-lo10
    

Two Wheels Better

Two Wheels Better
Moderator
Moderator
My elderly mum divined tea leaves, consulted the stars, and somehow always knew when I'd pranged on my dirtbike.


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1970 R60/5, OZ '77 R75/7-R100, '85 K100'87 K75C, OZ '87 K100RS, '93 K11-K12 Big Block, '93 K1100RS, '95 R100-Mystic, '96 K1100RS, '98 K1200RS, '00 K1200RS, '02 K1200RS, '03 K1200GT, '04 R1150R'04 R1150RT, '05 K1200S, '06 K1200R, '07 K1200R, '09 K1300GT & 2013 R1200RT-P  - Beemers owned still or sold.

~We all believe what we want to believe in - Rob Dickinson
    

roach374

roach374
Silver member
Silver member
@Dai wrote:(i.e. a wire that gets power when the ignition switch is turned on)

Ahhh, *that's* what that means. Thanks!


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1993 K75 standard
    

NayoAlex

NayoAlex
active member
active member
@robmack wrote:No, eso no es correcto. Conecta el positivo del alternador al positivo de la batería, el negativo pasa a tierra del marco y el cable azul para el devanado de campo pasa a través de una resistencia (que sustituye al indicador de carga) a una fuente de alimentación conmutada.
¿El valor de la resistencia es 100 ohmios 5w?
Gracias

    

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