Need Help w Fuel Gauge Please - Tried a Search

[DeadheadNM]

The fuel gauge in my 72 Blazer reads 1/2 full with a full tank and when I disconnect the tan harness wire from the fuse block the gauge needle swings way over to the 5:30 position. I didn't realize it could peg that far to the right. Could this be a grounding issue? Bad printed circuit?

Just before my recent move we swapped in a rebuilt all OEM cluster. Prior to that, the gauge was working fine when I drove the Blazer from So Cal to Albuquerque. The sending unit was replaced when the PO had the Hickey tank cleaned/coated. We didn't muck with the tank.

Appreciate any help. I was unsuccessful in searching for an answer.

Thanks, Pete