Bruce stated the correct info. The OEM 9N-12250 BALLAST RESISTOR was ONLY used with the FRONT MOUNT DISTRIBUTOR, '39 - '50. When thE ANGLE (SIDE) MOUNT DISTRIBUTOR was released, the Ballast Resistor became obsolete and the new side mt only used a junction block, p/n 8NNN-14458. Many fellas confuse the Ballast Resistor with the junction block and also if they add an external resistor in the circuit because they don't know how to wire a 12V system correctly. Guys get in trouble with their 6V setup, think they need to go to 12V, then get that all mucked up, so then assume (wrongly) the next step is to go to EI. As our late Sparkie Meister Dell always said ...if it won't start on 6V, what make you think it will on 12V??? Also, realize EI only replaces the need to use breaker points. Good for the electronically challenged and/or guys who don't have the patience to read the manuals, but know too if you wire one thing incorrectly with EI, you will fry the EI unit - a costly repair job. Perhaps this is why you had issues with the OEM 6V/POS GRN system as is the case with many. FACT: 99.98% of all non-starting issues are due to incorrect wiring regardless if 6V or 12V. It doesn't matter which system you want to use, just be certain you know what you are doing and you do it correctly. There are NO FORD manuals that detail the correct way to wire the 6V/POS GRN setup to a 12V conversion. Only s few gurus have created documents for correct wiring methods. One fella, Jesse Morris, created his WIRING PICTOGRAMS by JMOR document. Kevin LaRue also did sketches on 12V 1-Wire and 3-Wire Alternators. Best to invest in the original Owners manuals so you see the correct 6V setups and all the other systems to do PM on your tractor. There are but only one or maybe two correct ways to wire the 6V/POS GRN systems, and a hundred or more ways to wire them incorrectly, 12V especially. Here is the correct information on the FORD TRACTOR wiring systems:
NOTE: ALL Models used the FORD 6V/POS GRN Electrical System until the Diesel Models in 1957. The diesels used a 12V battery, a 12V Generator, and a 12V Voltage Regulator. 12V is always wired a a NEG GRN They still made gasoline models as 6V units. The 3rd most neglected part of electrical system failure is the lack of a fan belt tensioning bracket need to charge the battery plus operate the water pump correctly. You need proper fan belt tension regardless if using a GEN or an ALT otherwise you will never charge the battery. ALL 9N & 2N Models used a 1-Wire GEN with the ROUNDCAN CUTOUT. The Cutout is NOT the Solenoid. ALL 9N & 2N Starter Motors used a 6V, 1-Wire Unit with NO RELAY (SOLENOID). Beginning with 8N Model in 1947, the STARTER MOTOR now was a 3-Wire Unit with a RELAY (SOLENOID) fastened to the barrel of the starter, and now used a Voltage Regulator thru '64. BTW, starter motors don't care if 6V or 12V so don't think you need to swap yours out to 12V when going that way.
1939 thru 1950 = Front Mount Distributor; 6V Square Can Coil; 1-Wire. 9N-12250 Ballast Resistor required regardless if using 6V or 12V. Front MT points set at .015 and timing set per manual on your bench, BUT, mount it wrong on engine and you destroy the base. ALL FORDS use the 1,2,4,3 Firing Order. ALL N's use the CCW
rotation order. Beginning with the NAA, and all thereafter, rotation was now CW. With a front mount unit and doing a 12V conversion, if using the original 6V coil, you need to add an external 1-OHM resistor in-line in the coil circuit. swap out the 6V coil to a verified 12V coil and delete the extra resistor.
ORIGINAL 9N-12250 BALLAST RESISTOR, USED ONLY WITH THE FRONT MOUNT DISTRIBUTOR:
9N-10505-B CUTOUT:
FRONT MOUNT FIRING ORDER:
8N WIRING PICTOGRAMS by JMOR, 6V & THE 12V CONVERSION:
8N w/SIDE MOUNT DISTRIBUTOR USING A 6V COIL, NOTE INLINE 1-OHM RESISTOR:
8N & UP 3-WIRE STARTER MOTOR w/RELAY:
DELCO 10SI 3-WIRE ALTERNATOR WIRING:
Tim Daley(MI)
