minimax

Yes, Airportable. I came to the same conclusion based on thinking it out. Electronics engineers are gravely irked by misbehaving electrons but the diagnostic works like this: Sudden but intermittent loss of volts as monitored at the cabin voltmeter. Alternator voltage within limits:13.9 to 14.5, according to load. Volts there as soon as engine is running. Fault condition knocks everything out until key is turned fully back and then everything comes back on first position.

Cable goes from sound battery to starter motor then to alternator and from there to the rest of the car so the break occurs before the starter motor and is a hard switch off not a dimming phenomenon. Break is occurring at the starter connection. that reduces the volts seen at the cabin as there is increased resistance in the cable/ starter/alternator connection.

I reckon that must be it. Off with the K and N and in through the back rather than remove the hardtop and the engine cover.