[PSUBS-MAILIST] Earth Fault

[James Frankland via Personal_Submersibles]

No.  Just sat on the trailer.

On 27 July 2015 at 11:58, Alan via Personal_Submersibles <
personal_submersibles at psubs.org> wrote:

> James were they in the water?
>
> Sent from my iPad
>
> > On 27/07/2015, at 10:33 pm, James Frankland via Personal_Submersibles <
> personal_submersibles at psubs.org> wrote:
> >
> > Hi All
> >
> > I have a very peculiar issue.  I have an earth fault on the boat.
> >
> > My test consists of holding one probe of the meter on the positive
> battery terminal and the other to the hull somewhere.  I was showing a
> reading of 24v.  So obviously a negative connection somewhere to the hull.
> >
> > I went around everything taking things off and have tracked the fault
> down to the lights.
> >
> > The lights are the trustfire ones and the negative connection is
> grounded to the chassis of the light.  However, when I fitted the lights, I
> was aware of this and so insulated the mounting bracket from the  light
> casing itself with a piece of rubber.  So theoretically, there is no
> physical connection from the case to the hull.  Only the internal wire.
> >
> > Anyway, if I disconnect the lights and leave them dangling on their
> wires, there is no earth fault.  The lights all work, and the hull is clean
> of current.
> >
> > So the lights must be leaking back through the connection somehow, but I
> cant see how.  The case is insulated from the mounting bracket with rubber
> and the brackets are connected to the fibreglass faring, so it shouldn't
> leak back?
> >
> > Anyway, ive fixed it by insulating the mounting bolts with delrin
> washers, but I cant see how the earth could return through a piece of
> rubber and then glass fibre.  A mystery unless anyone can see something
> obvious?
> >
> > Regards
> > James
> >
> >
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