if the gauges are used originals, you might try a 3rd wink
if you know a gauge is good, then you should make sure you actually have power to it - the sender is a thermistor, heat causes variation in the resistance to ground, controlling the current flow thru the gauge .... so, a good gauge with power should jump when you ground out the wire to the sender - if it does, but doesn't work hooked up, it's a bad sender [don't use teflon tape installing a sender], if it doesn't move it has to be a bad gauge or no power [bad wiring some where, check continuity from gauge to sender, and voltage at gauge to ground]

Bill

Moved over to the Passing Lane

"When we tug a single thing in nature we find it attached to the rest of the world" John Muir
"When we tug a single thing on an old truck, we find it falls off" me
Some TF series details & TF heater pics & Rust-a-holics Unanimous parking lot