412 Electrical Problem

[sv8predator]

I would check all the main electrical connection forst in case there is a high resistance somewhere. So main battery cables (especially the earth) and the main cable to the starter motor.

Is there a separate heavy engine-to-chassis earth cable? Check that.

But a major problem with the regulator and the cause of intermittent faults is that the regulator BODY must be earthed, and earthed properly.