question on bulkhead connector bypass

Dave NEO said

That does clear up a few things for me thanks but that does not seem to explain how the VR can reduce charging current to battery when it needs to to prevent overcharging if there is a constant direct charging current to the battery from the alternator via the the starter relay connection.

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An easy way to tell how it would work is to run a wire direct from the battery+ to the blue on the regulator with the car running.
That would temporarily make that direct connection to the battery+ for the sense wire and show you what difference doing it with a relay would make before you go to all the trouble of doing it to find it made very little difference.

On my car it helped a lot, but it doesn't always.