electrical ??

["my69300" <tubman@xxxx>]

I have a fuel gauge problem.
I posted a week or so ago with the same
problem.The gauge is stuck in the full spot
when the ignition is on.I have tried to
trace the wires down to try and find
a break in the wire no luck.
So I was reading the service manual
and it said I need to use C-3826
tester.
My question is what the heck is a 
C-3826 tester?? And how do I get one?
HELP
Chris