Iam on my second set of gauges! That were previosly bench tested and worked good! However when assembled the gauges dont work!Is this a ground problem?

If they work on the bench they should work in the car, check the ground, hot wire and senders for them,
Best wishes,
T.

I have a similar problem with my ammeter in my 73 454 cid vette. Guage won't move, assumed it was broke...had it rebuilt and still no movement.

wired in an aftermarket voltmeter across the battery. shows fine voltage...

the guy that repaired my radio said there might be a ballast resistor in series with the ammeter to limit full current inside the car and that may be bad...

couldn't find sucha device on any wiring diagram,,,

any experts out there?

If it is your ballast resistor...it would be located on or close to your coil. I'm not sure what year your vette is.