Alternator Output problem

[PBBIZ2]

I have a GQ Nissan Turbo Diesel, fitted with an after market 200A constant duty alternator, externally regulated via a Sterling High Output battery management computer and low loss diode splitters. It charges and regulates flow to a starting and a deepcycle battery. It has worked faultlessly for 5 years. Today, a slight burning smell in cabin, for 5 secs then disappeared. 2 minutes later, whilst driving with lights on, noticed both deep cycle and starting battery voltages falling, both monitored with digital volt gauges. Alternator went from charging at 14.7V to gradual decrease. Approx battery voltage at trips end on first day was 12.4V. There was a slight smell or pong from under bonnet when bonnet lifted, like burnt windings?.

Was going away for weekend, so continued. Main battery voltage dropped to 6 volts, aux stopped dropping though, all accessories turned off. Pull car over and transferred cables from splitter to starting battery over to deep cycle. This equalised out voltage, but only getting 11.7V from back of alternator, at idle and revs. Battery voltages did rise for a short period then settled at 12.4V before falling again to 12.0V over a 1 hour drive home.

Turning indicators on, or applying brakes resulted in voltage dropping further, so alternator either not charging or other fault?

Is this likely to be an alternator problem, faulty battery or perhaps short on main starting battery side? I know, could be all of above, just trying to cut some time out of the issue.


Any help appreciated

thanks Phil

[PBBIZ2]

Problem discovered, fried wire on back of alternator lerading to regulator. Might have done a bit more damage though than expected.

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