Old or New Fuel Sender?

Had the factory sender in my demon and about a year after the resto it went,

what went wrong with it?
it is just a mechanical variable resistor and i don't see how it could fail?
..did the wire come off?

I wish i knew, it wasnt reading one day, grounded the plug and gauge went to full so i knew gauge was good, ground strap was tight and everything seemed right, i just figured the sender contacts were wore, maybe i should of kept it, ill have to look and see if i did