[Ozarkguy]

Yep thats the Shunt. The black wires are going to the individual fuses. The red wires are going to the Ammeter. You should check each fuse for continuity. (remove the wires (look out for sparky!) If the fuses are OK ... try reversing the leads on the meter.. If it goes the other way the meter should be ok.. That would only leave an open in the wire. You said you have power to both sides of the meter.. but if you have one bad fuse the power will feed thru the meter ..
You are measuring FLOW not Power....with the ammeter