I've got a 1969 Javelin. New gas sending unit. I've got continuity from cluster plug to sending unit connector. Tested gas gadge also and it workes, Also tested circut board and it is good. Yet the gas gadge still doesn't function. Tried running seperate ground from gas tank, no luck. Also have did same procedure for temp sending unit with all same results. Need help
Might be a bad gas gauge
same with temp gauge. If you ground out temp sending unit wire does the gauge move to H. If it does then there is a problem between the two or the voltage regulator for dashi s no good. See if your green wire going into the dash if pin is marked it should be #6 that is power feed to gauges. Then check the fusible link in pic i'm sending.
Sounds like you don't have voltage feeding the gauges. Look for a voltage regulator plugged into the back of the cluster. It cycles on and off like a signal flasher.