The Stovebolt Site Forums The Shop Area The Electrical Bay Universal wire harness

I don't remember and did not go over all of this post BUT..........

The harness is not set up for a reducer, it is set up for 12V. So by following the instructions you attached the correct red wire to the ignition switch and per instructions you attached the correct red wire to the gauge. Normally the harness and it's fuse panel takes care of the circuit.
HOWEVER......you have a reducer. So, how did you hook up the reducer? You probably put it in series on the wire to the gauge? Is that what you did?

If that is the situation, take off red wire at the gauge, turn on ignition switch and put a tester between disconnected end of red wire and a good ground. (this would be after the reducer). Should get 6V. Then put tester before reducer to good ground. Should get 12V. Report or ask more if not sure.

"Am I supposed to ground IT at the gauge cluster also?" WHAT IS "IT"?

"Or do I run a wire from the ignition to the fuel gauge like the 47 wiring diagram shows." Don't think so.

If you don't have power on the end of the wire to the gauge, nothing else matters.