In article ,
Bill Janssen wrote:
I think the key to an explanation is that the cut out relay senses
current direction as determined by referencing the magnetic field of
the current to the magnetic field of a voltage fed electromagnet.

Since both were reversed the cut out relay didn't have a clue as to the
polarity.

I hope I explained my thinking clear enough.

In the UK, when I were a lad, most cars were positive ground. This of
course made no sense to the average punter, and it was very common for the
clueless to fit a new battery the wrong way round. And the symptoms were
the battery didn't charge.
As electronics became more popular, the change was made back to negative
ground for new vehicles. And if the owner of an older vehicle wanted to
fit a modern stereo, the easy answer was to convert it to negative earth,
and I've done dozens. And always had to re-polarise the dynamo before it
would cut in and charge. If the cut in had operated with the battery the
'wrong' way round, that would have re-polarised the dynamo and made this
unnecessary.

Of course, this was with the infamous Lucas electrics. Could be that other
makes work differently.

--
*Sometimes I wake up grumpy; Other times I let him sleep.

Dave Plowman London SW
To e-mail, change noise into sound.