Something ain't wired correctly on your setup the way it is. What is the ceramic resistor fastened to - the switch, cutout, or the ammeter? Your 2N has the front mount distributor. It also has the square can coil and the OEM Ballast Resistor. They also use a 1-Wire/3-Brush 11 AMP generator with a roundcan cutout circuit (behind dash), and a 1-wire starter motor with NO solenoid. Is there a problem with your 6V/POS GRN system? It's your tractor and you can whatever you wish, and there is nothing wrong with a 12V/NEG GRN setup, but many newbies (and a few oldies who don't know) think a non-starting issue is due to a 6V system. Basically, they just don't understand and don't have the time to think it thru logically. There can be many reasons why it won't start, regardless if 6V or 12V and 99.98% of them are due to incorrect wiring. If it doesn't run on 6V now, what makes you think it will on a 12V switch over job? If you don't already have them get the Essential Manuals. ALL 9N/2N, and early 8Ns use the front mount distributor, square coil, and the Ballast Resistor. When one changes out from a 6V POS/GRN setup to a 12V/NEG GRN system, you still use the Ballast Resistor, and coil but need to add the white ceramic 1-OHM resistor in the circuit ONLY IF you are using the OEM 6V coil. You can get a 12V coil and not connect the in-line resistor at all - as many have recommended. On a 9N/2N you need a 12V battery, new 12V battery cables, new 1 or 3 wire alternator with tension bracket, new belt, and remove the generator,cutout, 6V battery, and cables. You will also need to consider a new wiring harness at this time.
FORD TRACTOR 9N & 2N OEM 6V/POS GRN WIRING:
<img src="https://i.imgur.com/QWaC1aah.jpg">
<img src="https://i.imgur.com/CJedLEch.jpg">
FORD 9N & 2N WIRING 6V & 12V:
FORD N-SERIES TRACTOR FRONT MOUNT DISTRIBUTOR 9N-12250 BALLAST RESISTOR:
EXTERNAL IN-LINE 1-OHM CERAMIC RESISTOR ? REQUIRED WITH THE FRONT MOUNT DISTRIBUTOR WHEN USING A 6-VOLT COIL:
FORD 9N-10505-B CUTOUT ?USED AFTER S/N 12,500 TO S/N 258504 ON 9N & 2N MODELS ONLY:
*NOTE: When doing a 12V switch over job, the cutout is eliminated along with the generator.
FORD 9N/2N TRACTOR ESSENTIAL OWNER/OPERATOR/PARTS/SERVICE MANUALS:
Tim Daley(MI)