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

[Doug Tallman]

At 10:42 AM 9/11/04 -0700, you wrote:
>My Massey 175 fuel gauge is not working.  Can any of you electronic wizards 
>suggest how I might determine whether the gauge or sender unit is bad 
>(without buying both new parts for a try)?  I have an ohm meter but don't 
>know what to do with it with what I guess are resistances involved.    I'd 
>like to fix the bad unit while I have the tank out.     John
>
>                    In the wide-open spaces of NE Oregon
>_______________________________________________

John, just think of the sender as a variable resistor. With it unplugged,
ohm check between the lead and ground. Most automotive systems run 0-90
ohms through the range of the sender. Move the lever by hand and see what
you get. On an automotive system, a test light between the lead coming from
the guage and ground would be steady dim or blinking (depending on mfg). It
will usually make a good guage read between 1/4 and 1/2 tank depending on
the bulb. As Farmer always says: Check The Grounds! If the sender grounds
through the tank and the tank has insulators where it sits, it has to have
a ground from the tank to the tractor. Clear as mud? Maybe it will at least
get you started.


                                                      
           Doug Tallman                 
           dtallman at accnorwalk.com                 
           VGTCOA Ohio Regional Director  
               Greenwich, OH USA