Larry,
wouldn't that suggest that your new gauge is an "ammeter type" as Bob
mentions?
Ulix
On Tue, 29 Jun 1999, Larry Miller wrote:
> This is all well and good, but, based on all of this, can someone explain
> why my gas gauge works backwards? I just assumed it was hooked up backwards
> and have not bothered to swap the wires. Now I'm afraid to swap them.
>
> The gauge is a new Smith's gauge and the connections are not marked "T" and
> "B". They have no markings at all.
>
> Larry Miller
> http://www.ado13.com
> "If you want a Sprite, start out by asking your wife for a Porsche."
>
>
>
>
>
>
> ----- Original Message -----
> From: Wiedemeyer <boxweed@thebest.net>
> To: Pete <pete@the-mix.com>
> Cc: spridgets list <spridgets@autox.team.net>
> Sent: Tuesday, June 29, 1999 7:31 AM
> Subject: Re: Fuel gauge polarity?....Old Dog, New Tricks
>
>
> > Frank and Pete,
> >
> > After reading about your experience with frying the sender unit after
> > reversing the wires on the fuel gauge, I just had to find out why this
> > happens. I had mistakenly believed that the fuel gauge was a simple
> ammeter
> > parallel type arrangement where the needle draws a very tiny amount of
> > current for deflection while the bulk of the current is shunted through
> from
> > one pole (B) to the other pole (T). If this were the case, reversing the
> > wires would cause the needle to deflect in the opposite direction, but
> would
> > not result in more current going through to the tank. After looking up
> how
> > a fuel gauge actually works, (in Automotive Encyclopedia by Toboldt,
> > Johnson, and Gauthier -- $48.50 and worth every penny) I now see why
> > reversing the wires will burn out the sender unit: The fuel gauge is a
> > "thermostatic gauge", which has a very large resistance in series between
> > the B and T poles. This reduces the current that ultimately gets to the
> > sending unit. If the wires are reversed, the large resistance is bypassed
> > and much more current goes directly from the battery to the sending unit,
> > which fries it. The idea behind the thermostatic gauge seems ingenious
> to
> > me because it uses the heat accummulated in the resistor to warm up the
> > bi-metal fuel gauge needle, which causes it to move when the ignition is
> > turned on. There's never any current "felt" by the needle, which would
> > explain why the fuel gauge itself almost never fails. I guess it's never
> > too late to learn something new.
> >
> > Thanks,
> > Bob
> > -----Original Message-----
> > From: Pete <pete@the-mix.com>
> > To: Frank Clarici <spritenut@Exit109.com>; Wiedemeyer
> <boxweed@thebest.net>
> > Cc: Doug Ingram <dougi@home.com>; spridgets list
> <spridgets@autox.team.net>
> > Date: Tuesday, June 29, 1999 9:56 AM
> > Subject: Re: Fuel gauge polarity?
> >
> >
> > >
> > >>> Yeah. Just reverse the wires when attaching them to the gauge.
> > >>>
> > >>
> > >>Doug
> > >>
> > >>Yes it will work but DO NOT REVERSE THE WIRES!!!!
> > >
> > >>If you flip the wires on the gauge you send 12 volts to the sender which
> > >>is grounded + connected to - = smoke!
> > >
> > >I can vouch for that.
> > >Reversing the wires would be like putting the battery in backwards (yes,
> > >I did that)
> > >and frying your negative earth tach instantly (yes I did that)
> > >
> > >I am learning a ton though.
> > >
> > >Pete
> >
> >
>
Ulix __/__,__ ___/__|__
..............................................(_o____o_)....<_O_____O_/...
http://students.washington.edu/~ulix/ '67 Sprite '74 X1/9
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