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What is the D+ lug on the K1 Bosch alternator for? It was jumped over from the B+ lug when I inherited this boat. It had a parasitic drain on the battery that was identified as the alternator. First suspicions and advise was that a diode was bad. But, I am now thinking the jumper wire from the D+ lug was the cause. I “now” understand this to be the field exciting lug also used in conjunction with a charge indicator light. The light fed from the ignition switch excites the field which when running then has zero potential with the B+ lug. This will extinguish the light when running, but when not the field is grounded or close to it causing current flow.
Should this D+ lug be fed off the ignition either the same lead that goes to the fuel solenoid (purple) or another charge indicator light run outside of cummins wiring loom.
Engine is an older 250hp 6bta JWA.
Also, how do I determine the current rating for the alternator? I believe it can be 95 or 120 amps. AL9971N / AL9972N
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