On 26/04/2021 08:34, Brian Gaff (Sofa) wrote:
Surely though there is always some drain from the vehicle battery due to all
its electronics running.

It's thirty years old! Electronics wasn't invented!

So that small drain may not be an error.
It must have quite a complex switching set up, probably with some logic
built in in any case and it would be interesting to know which circuit it
uses to keep this running.

The only thing is, the 12V circuit powers the LEDs that light the
ammeters and voltmeters.

Bill