Thread: 10SI voltage regulator fails repeatedly

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JMHO, but it appears to me you have two issues;
1) Excessive current draw after the ammeter. I say after because the ammeter only register the current draw going through them, and ammeters are usually wired on the accessory side of the circuit (no starter load).
2) The regulator is not operating/sensing correctly causing a high output voltage (15+ volts is too much).

Believe it or not, both conditions can be caused by poor/bad connections, including but not limited to grounds. A poor connection causes resistance, in turn lowering the voltage to the appliance (what it is connected to), causing current to rise. A bad MAIN ground connection can cause the regulator to increase voltage as it's sensing through the resistance and adjusting (additionally the ammeter would read high).

Try grounding your alternator directly to the battery (jumper cable), if the alternator's output voltage drops to an acceptable voltage (14 -14.7 volts), then you have a poor ground connection between the battery and alternator. It may be at the motor where the battery ground connects.

I personally do not like the idea of 100+ amps of electrical current seeking ground through my motor (and its moving parts).

I run separate grounds to every electrical appliance, especially when connected through the motor. Alternator, A/C, Fans, cylinder heads (yes spark is and appliance), exc.. Some will say this is over kill, and in some cases (stock) they may be right. I'm not a gambler, and I've seen what current can do, so I ground everything....

Good luck