Author Topic: Bosch charging system question  (Read 292 times)

Online Scout63

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Bosch charging system question
« on: September 25, 2021, 05:21:00 PM »
How do I test my Bosch (G5) alternator for AC voltage output?  Do I ground my volt meter on the stator frame and test the three output terminals?  The stator and rotor both static test fine for resistance across the slip rings and stator output points. Iím chasing down an aftermarket reg/reg that is not charging the battery.  I think itís wired in right.  If the alternator is outputting ok Iím going to wire in a spare to test. Any feedback is welcome but please donít ask me for a diagram. Iím just too lazy.
Ben Zehnder - Orleans, MA USA
1971 BMW R75/5
1972 Norton Commando Combat Interstate
1973 SL 125 so very rusty
1973 V7 Sport
1977 BMW R100S
1977 LM1
1978 Ducati 900SS
1978 Yamaha SR500
1979 V1000G5

Offline Kiwi_Roy

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Re: Bosch charging system question
« Reply #1 on: September 26, 2021, 12:24:40 AM »
Test for AC Volts between any two of the yellow wires, any two should measure the same.
If you dont get at least 20 Volts at 2000 revs then check the DC Volts across the rotor brushes.
The AC Voltage on the Stator is proportional to the Voltage across the rotor for any given speed.
You might find some useful information here, they will certainly have a suitable regulator. https://www.electrosport.com/pages/technical-resources
I used an ESR450 on my California II, I like it that they replace the old loom with new conductors.
« Last Edit: September 26, 2021, 12:30:46 AM by Kiwi_Roy »
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Online Old Jock

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Re: Bosch charging system question
« Reply #2 on: September 26, 2021, 03:35:03 AM »
As usual Roy nailed it.

The way I'd do it is to disconnect the 3 yellow wires then test across the 3 tabs that the yellow wires plug into, I've just always did it with alternator open circuit, I've never tried in circuit, but it should also give you a high AC voltage, with that voltage rising as revs increase.

Probably something around 35-40V AC at 3k and they should all be identical.

John

Online Scout63

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Re: Bosch charging system question
« Reply #3 on: September 26, 2021, 09:38:55 PM »
Thanks thatís just what I needed.
Ben Zehnder - Orleans, MA USA
1971 BMW R75/5
1972 Norton Commando Combat Interstate
1973 SL 125 so very rusty
1973 V7 Sport
1977 BMW R100S
1977 LM1
1978 Ducati 900SS
1978 Yamaha SR500
1979 V1000G5

Wildgoose Chase Moto Guzzi

Re: Bosch charging system question
« Reply #3 on: September 26, 2021, 09:38:55 PM »


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Harper's Moto Guzzi. Where we still answer the phone, use the highest quality parts, and also do Transmission, rear drive, and carb rebuilds fast. Call us at 816.697.3411 and get your problems resolved.
http://www.harpermoto.com
Advertise Here