BudL

Hi guys (&gals)
I am troubleshooting erroneous fuel gauge indications. I have a maintenance manual and according to the troubleshooting chart I probably have a bad connection or a break in the yellow wire since I have no voltage at the wire at the tank. From the wiring diagram it looks like I should have 12v at the tank on the yellow wire. Is that correct?

I know that some cars run the gauges through a step down transformer and I don't want to be looking for 12v when it should be 5v. The car is a restomod and the wiring harness is American Autowire so the wire colors don't necessarily match the wiring diagram in the manual.
FYI, the gauge seems to be approx. correct down to about 1/2 tank but it doesn't go much lower than that. The sending unit has been rebuilt.
Any help would be appreciated and thanks to Joe for his previous assistance via messaging.
Bud