I have a 1953 3100 that I am rewiring. I'm doing it all myself. I'm following the old wiring harness and a diagram. Anyway, I hooked up all the dash wiring and starter circuit, ign. switch, etc. Started the truck and it ran fine. However, the ammeter read DISCHARGE when I revved the engine and ran a slight CHARGE at idle. Everything seemed to be hooked up right. What is the (+) and what is the (-) side of the ammeter? I'm no electric guru but I feel confident in the harness I'm constructing. The wire gauge is correct and all the connections are soldered with shrink tubing added. Is the gauge bad? Looking for some ideas. How should the gauge read normally. I did have a gauge in the truck that read a CHARGE upon acceleration. The new gauge is giving me a different reading.

1953 3100 | 1958 3/4-ton NAPCO