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

H. L. Staples hlstaples at mcloudteleco.com
Wed Sep 15 11:12:44 PDT 2004


Steve you are correct in that Guage circuits are not all operated at full 12
volt.  One of the reasons is if the design was for 12 volt,  then any drop
in voltage, low battery would cause the readings to be off.  The last system
I was into was our old 77 F250.  It has a small voltage regulator built into
the flexible plastic panel behind the display.  As I recall the operating
voltage is 5.5

John if the sending unit is erratic in operation,  pry it apart that is bend
the little tabs so the metal housing can be separated from the base and
check the tension on the little wiper arm and if necessary do a little
adjusting with a small set of pliers.  You can check for continuity with the
ohm meter, the movable contact is attached to one end of the variable
resistor. 
 
H. L. Staples
McLoud, Oklahoma 
USA
 
-------Original Message-------
 
From: Antique tractor email discussion group
Date: 09/15/04 09:27:33
To: Antique tractor email discussion group
Subject: Re: [AT] How to test a fuel gauge/Sender??--Rickey
 
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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