Farmall M charging system question

Ok Guys, here is another question on my Farmall M. I just got this tractor recently. Someone had rewired the tractor with all the same color wiring! They had attempted to convert it to a 12 volt system but still had a 6 volt generator on it. I put the tractor back to original 6 volt system, with a positive ground, replaced the voltage regulator,and the ammeter, which wasn't working, and the tractor seems to be charging but the ammeter doesn't move either way, even when you use the lights. Can anyone tell me what to check for? I have the same problem on a John Deere B, and am sure that the ammeter is a good one. I'm not an electrical genius so I need a little advice! Thanks for any help!

Perhaps the ammeter isnt wired correct?? (may have got rewired if battery polarity was reversed) Theres usually just ONE wire on its SUPPLY terminal that connects to the battery/starter for the main hot battery feed/connection and over on its other LOAD terminal it wires to the BAT terminal on the Voltage Regulator PLUS can feed hot battery voltage to lights and ignitiion via a wire from the ammeters LOAD terminal to the switches BAT input terminals. If the batetry and loads are on the same side of the ammeter it doesnt read correct...

Then if its wired correct n shes not running if you turn on lights it ought to swing over to - discharge. if it swings to + charge its wired bass ackwards n needs its leads swapped. When the battery polarity was reversed the ammeter leads needed swapped to make it read correct, maybe it never got rewired correctly after that????

To see if shes charging place a voltmeter on the battery and it should read around 6.3 volts setting there but when running at fast RPM it should raise to the 6.5 to 7 volt or so range. If it does that its indeed charging even if the ammeter isnt wired correct.....

John T