Hello Peter and Volrem, thank you for the posts and sorry for my late reply.
I am also intrigued by the voltage values between both vehicles.
The good vehicle has battery voltage above control voltage whereas the faulty vehicle has the reverse! (Battery voltage lower than control voltage)
I would like to know more about alternator load under these conditions and so would like to see current from the alternator to battery.
Could we also include the exciter/warning light circuit on our remaining channel and more time on screen as Volrem mentioned. (200 ms/div minimum)
Here we can see the activity of the complete system from idle no load, free rev no load, idle loaded and finally free rev loaded.
The idea here is to get an overview of the charging control under various load and speed conditions.
The best scenario would be to carry this out on the vehicle without any faults but we have to be realistic.
You mentioned volt drop tests, could you confirm this applied to the alternator charging cable form ALT + to Battery +
Just reading this through, can you take control of the control signal via a scan tool (Active test)?
Not sure if this vehicle has such a facility but we could see alternator response to independent control.
One final note, can we check the alternator response to disconnection of the control signal wire as with the case study below. https://www.picoauto.com/library/case-s ... tion-error
This may implement a fail safe (machine sensed) voltage control from within the alternator, so assisting with diagnosis
Any feedback will be most interesting, take care.......Steve