Actually, there is a voltage regulator behind the dash that supplies voltage
to the Fuel Guage. It delivers a constant regulated voltage ( I think
around 9 volts, but I'm not exactly sure). Tap into the light green w/green
tracer wire. You need to use this as the source for the supply side of the
temp gauge. If you try to run your electric temp gauge from a 12v source,
the readings will be false, and on the hot side, and they will vary,
because, sometimes, your 12v system is actually at 14.2 volts, and then when
your heater fan, headlights, and wipers are all on at the same time, you are
at 12.8 volts.
David Riker
davriker@digitalpath.net
http://community.webshots.com/user/fool4mg
http://www.myspace.com/fool4mg
----- Original Message -----
From: "Gregory Groiss" <ggroiss@gmail.com>
To: "Chris King" <cbking@alum.rpi.edu>
Cc: <spridgets@autox.team.net>
Sent: Monday, August 14, 2006 5:03 PM
Subject: Re: Temp Gauge Wiring
> Thanks Chris. As soon as I hit send on that last email I realized it
didn't
> make sense to have the other terminal as a ground. I figure I may be able
> to tap into the power from the fuel gauge. Doesn't it work in much the
same
> way?
>
> Thanks again,
>
> Greg
>
>
> On 8/14/06, Chris King <cbking@alum.rpi.edu> wrote:
> >
> > You need a +12V supply. Remember, the sending unit is just a variable
> > resistor (the resistance changes with temperature), and the gauge is
simply
> > an ohmmeter in series.
> >
> > In other words, its: +12V ---> gauge ---> sender ---> ground.
> >
> > In this case, ground is the engine, where the sender is screwed in to.
> >
> > You can probably get +12V from one of the green wires on the dash
harness.
> > If you have a Haynes manual, you can double check against the wiring
> > diagrams for the '78 and '79 Midgets.
> >
> > Hope this helps.
> >
> > -=Chris
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