On 9 Sep 2002, at 14:54, Bill N wrote:

> If the fuse protected the wires before, it will still do it.  The wire size hasn't shrunk.
>
> Bill
>
> ----- Original Message -----
> From: "Chris Mills" <scmills@TNTECH.EDU>
> To: <vanagon@GERRY.VANAGON.COM>
> Sent: Monday, September 09, 2002 12:09 PM
> Subject: Headlight upgrade questions
>
>
> >
> > I upgraded my '78 Westy headlights using the ever popular relays feeding
> > directly from the battery via an aux. fuse panel.
> >
> > Now that my headlight switch is only driving the headlight relays and the
> > toggle relay (high/low beam) - - should I reduce the fuse for the original
> > circuits? The new headlight circuits are fused at a new fuse panel out back.
> >
> > I'm thinking a pretty major short to ground would have to occur to blow the
> > OEM fuses at 8 amps - enough to melt the wiring before the fuse blew.
> >
> > Chris M. <"Busbodger" of "TEAM SLOWPOKE">
> > Cookeville, Tennessee
> >
> > ICQ# 5944649
> > scm9985@tntech.edu
> >
> > '78 VW Westfalia (67 HP -> that is...67 Hamster Power)
> > '65 Beetle - Type IV powered
> > '99 CR-V AWD station wagon
> > '81 CB900 Custom moto-chickle
> > 2.5 Corvair engines for my Trans-vair Conversion
> >
> >

Bill,

You're right that the 8 amp will protect the wiring - as it did before.

But an even more fundamental purpose of fuses is to prevent fires,
regardless of wire size.  Can there be a fire without drawing enough
current to damage the wire?  You bet!  The probability of that happening
can be reduced (but not eliminated) by reducing the fuse size to the
minimum necessary.

Someone on this list, a month or two ago, described a situation where he
discovered a defective wire terminal connection in his vanagon (fuse
block?).  The crimp connection was bad (high resistance) and was heating.
Ifirc, it was getting close to where it could have started a fire.  The
circuit fuse had not and may not have blown until after a fire was
initiated (and a true short developed), but by then the fire may have been
self-sustaining.  None of this had anything to do with wire size.
However, the lower the fuse rating the quicker it would have blown as
heating & charring developed and shunt impedance decreased.  Would a lower
rating have saved the day.  I have no idea ... but maybe.

OT, but possibly of interest is that home electrical codes (U.S.) are
moving toward requiring a special type of breaker in the home, I think at
first for all bedroom circuits.  This special breaker will sense arcing
such as that which occurs at poor connections.  I don't know much more
about it yet but I think that illustrates that the danger I've referred to
above is taken very seriously.

//Jack