Hi I've been refinishing my dash and am currently reassembling everything. Went to test dash lights and gauges and the tach goes to 10X rpm but doesn't move from that point when I press the accelerator. Also my fuel gauge doesn't work. I wonder if i plugged something in backwards. I've check the grounds on the back of the metal dash and they are secure but if the dash isn't fully installed is the cluster not grounded?

 

As I recall, yes, the dash needs to be mounted to be grounded.

Run a piece of wire from the metal dash plate to a good ground point on the car and see if anything changes.

Cheers
DD