the temp sender and wires are actually a thermocouple. There are two wires to
and in the sender that are not the same material. At different temperatures the
two materials act like a battery and gives the gage different readings. The
problem is when someone cuts one or both of the wires in an attempt to shorten
or repair them. Then there are possibly three materials if the wires were
soldered and a bad connection if the were not. Of course it could also be the
gage but look at the sender and wire first.