["QUICK-SILVER"]

Originally Posted by 1971GTO

OK,

Alligator clip end at the blue wire, key on, test light end to ground at the hood; a little bit of light from the test light, but absolutely no action from the gauge.

Loose wire at the printed circut end at the gauge?

Doesn't really sound like a lose wire, test light wouldn't/shouldn't have lit at all. You've got power to the guage and coming out the sending unit blue wire so you should be able to make the guage do something.
With key on, touch the blue wire straight to ground and see if the guage moves. If you get no movement then the guage is probably bad. While the blue wire is grounded try to peck on the guage to see if the needle is stuck.
Keep us updated so will know if we need to come up with some different tests.

[1971GTO]

Will do tomorrow.

Later.

[1971GTO]

I took and grounded the blue wire to a hose post clamp with the key on. I used a bristle from street sweeper brush as the bridge. Tapped the guage at he plastic and nothing, is this a good enough ground?

["QUICK-SILVER"]

hose post clamp? you lost me there.
Good contact with bare metal touching the engine should work. If it was and guage didn't move it's time to get in the dash.