I installed a brand new dash harness a few months back. I finally was at a point over the weekend where I could test everything. All worked just as they should with two issues. The fuel gauge pegs at full with about a half a tank in the car and the oil pressure also reads kind of high even with the power off, The harness was for an a body with gauges so I'm assuming that the connections behind the gauge cluster are correct for that option.
The bigger issue is that all fuse connections at the block show power on both sides of the fuse except the small 4 amp instrument panel lamp fuse. I get no power there at al.. Electrical stuff is a real weakness for me so I have no idea what to do at this point. I would appreciate any and all guidance.

 

The instrument panel lamps are powered by the taillight circuit. No taillights, no dash lights. Try it again with the headlights turned on.

The full gauge will read past full with the sending unit unplugged, or the tank is ungrounded.

 

Matt,

You nailed the problem on the first try! The rear bumper isn't even on the car yet so no taillights! I will need to check on the other issue this weekend at the body shop. Thanks so much.

 

Sorry, that is not correct. The fact that the rear bumper is not on the car has nothing to do with the 4A fuse. Look at the wiring diagram. The 4A fuse does NOT get power from the battery. It gets power from the headlight switch rheostat. Power comes into the headlight switch then comes OUT of the headlight switch and runs to the fuse box to power the 4A fuse. This is how you dim the instrument lights.