I have a charging troubleshooting procedure but its for Class A systems yet some Fords are Class B. With your new info I suspect a charging or genny or regulator problem or the battery has been reversed!!!!! !!!!! ! Has the battery been changed and ground reversed? If so it wont charge right until the genny is correctly re polarized. If it swings to + charge that sounds like a meter that's wired backwards ORRRRR RR the battery is reverse polarity then original. Normally if its working and in the center but you turn on Ignition (NOT cranking, just ON) it should swing to a slight NEGATIVE DISCHARGE as the coil draws around 4 amps. If it stays in the center with nothing on and if a magnet will cause the needle to move both ways back and forth, I wouldnt necessarily say the ammeter is bad!!!!! Make sure the battery is properly charged as I have seen batteries charged backwards, Possible if the battery was COMPLETELY dead and the charger hooked up wrong.īased on this new info, I CANT SAY FOR SURE THE METER IS BAD. If it is a 'normal' gage the wires will be fastened directly to studs sticking out and if the battery is charged properly and hooked in correct polarity the gage can be reversed by simply moving the wires to the opposite studs. If that is the case reversing the wire in the back of the gage may straighten it out. Some of them older Fords had a ammeter that the charge wire simply passed through a round loop on the back of the gage, if the wire is going through the loop in the wrong direction the polarity could be right but the meter still read backwards.

when the switch is turned on sounds to me like the polarity of the system is reversed and the needle moving to full discharge when running could be indicating a proper charge but in reverse as far as the gage is concerned. If the needle centers I wouldn't be so quick to replace it, the needle moving to Pos. Quoting Removed, click Modern View to see

Battery charger needle not moving