68 roadrunner with standard dash..

My fuel gauge does not work. I have a new tank and sending unit. I would ground the sender wire and the gauge still does not work. I tried 3 different voltage regulators,in the center spade position on the backside of the dash.

I hooked up an autometer fuel gauge and that works great (used the factory sender wire) .

Want to get my stock dash working, so i bought another complete cluster which the seller said has working gauges. I still cannot get the gauge to work on even the new dash.

Obviously my sender wire is working becuase it feeds my autometer gauge. I tried adding another ground off the cluster and still no good.

Whats the chance of having another bad fuel gauge? Is there a way to bench test a fuel gauge.
Im running out of ideas and the dash is a pain to take apart...