Bosch charging system question

[Scout63]

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. I’m chasing down an aftermarket reg/reg that is not charging the battery.  I think it’s wired in right.  If the alternator is outputting ok I’m going to wire in a spare to test. Any feedback is welcome but please don’t ask me for a diagram. I’m just too lazy.

[Kiwi_Roy]

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.

[Old Jock]

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

[Scout63]

Thanks that’s just what I needed.