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

[John Wilkens]

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