Disappearing Fuel Level

1973 Duster, re-wired with a Speedway 21 circuit kit that is like a lot of other universal kits.

With the gauge cluster plugged in and sitting on my lap the gas gauge work fine. When I install the cluster in the dash, the fuel level drops to zero after a few minutes. I have recreated this in my lap by connecting a wire between the metal cluster mounting point to the metal dash. I have a ground wire from the wiring harness connect to the back of the cluster already and the arrangement is similar to the American Autowire classic update harness. I believe that wire was for the light ground. I wouldn't think an additional ground would make the gauge stop working.

https://www.americanautowire.com/PDFLink/92971259 510605 IN 0.0.pdf