[AT] How to test a fuel gauge/Sender??--followup

[John Wilkens]

Well, I've come the the disturbing conclusion that fuel senders and gauges 
are not as simple and straight forward as I thought!!   My ohm meter has 
shown me that my sender is kaput, but testing the gauge..........that's 
another matter!     I'll go ahead and order a new sending unit and hook it 
up to the meter with the original wiring hookup and see what happens.  At 
least that should not burn something up.  I just might take a used up AA 
battery like Mike suggested, short it out until there's next to nothing 
left in it and touch it across the guage terminals briefly to see what 
happens.  I hate to be bettered by a mechanical thing!   Never anticipated 
the volume of responses on this question, and I sure appreciate it.  Hope I 
didn't cause any serious problems!     John




At 07:07 AM 09/15/2004, you wrote:
>Not on most of the ones I have worked on. GM fuel senders run from 30-90
>ohms, Ford uses a 120-0 unit in many trucks while autos depend on the
>model. The one on my motorcycle tests good with 500 ohms full and 2K
>empty.
>It all depends on what they used. Oh and other than the ammeter itself
>99% of electronic gauges are VOLT meters not Ammeters as you stated
>Walt.
>
>
>Testing many meters and sending units is easy with a VOM though. The
>meter winding is usually OK if it tests as close to zero ohms across the
>terminals.  The sender is usually ok if when checked across the
>terminals you get a continuous smooth altering resistance as the senders
>probe is moved. On most you can test them easily IF you have the system
>apart by connecting the sender and gauge up and applying the normal
>operating voltage to the units, then watch the gauge as you move the
>float. Nice smooth motion across the scale and you OK.
>Be advised that there are quite a few vehicle fuel gauges that do NOT
>use 12 volts even in a 12 Volt system. Ford used 6 volt gauges in there
>trucks up until 92-93 and some tractor manufacturers did the same.
>
>
>Steve Williams
>Near Cooperstown NY
>
>
>----- Original Message -----
>From: <DAVIESW739 at aol.com>
>To: <at at lists.antique-tractor.com>
>Sent: Wednesday, September 15, 2004 2:22 AM
>Subject: Re: [AT] How to test a fuel gauge/Sender??--Rickey
>
>
> > Phil,
> >  I also have spent a lifetime of working on all kinds of vehicles and
>I have
> > never in 40 years of this ever found a gauge that would not take  full
> > battery voltage. If your right then I would be afraid to turn on the
>key because if
> > the sending unit is at 0 resistance then blooey.  By the way  almost
>all
> > sending units go from 0 to Max resistance.  You may call  yourself an
>expert but
> > your writing on the subject tell something different,  sorry but
>that's just
> > the way it sounds. By the way its not voltage that will  burn the
>gauge out but
> > amperage. You can 1 million volts though a tiny wire if  you have very
>little
> > amperage.
> > By the way do you know what the definition of 1 volt is.
> >
> > Walt  Davies
> > Cooper Hollow Farm
> > Monmouth, OR 97361
> > 503 623-0460
> >
> >
>
>
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                    In the wide-open spaces of NE Oregon