Guages intermittent issues need Help

Hi Gang, In my 70 swinger I have a Ralley dash, the one guage that has the Fuel, Oil Pressure and temperature has electrical issues.

For some reason, always on startup cold it always works, within 10 to 15 minutes, they all shut off. I have gone in behind to check connections and all are very clean with good power and ground.

I checked the capasitor and it works fine, even changed the capasitor and same thing, any ideas ?