Round coil vs square coil

Round 12 volt coil 3.8 ohms. NAPA product.(No external resister required)

Square 12 volt coil 3.3 ohms. YT product. (OEM style)

Read somewhere on this forum that the OEM resister (A8NN12250A) is not used when converting from square coil
to round coil.
Why not leave it in the system?
Asking for a friend.
Thanks,
Tom/Idaho

See tip # 30.

I've never seen a square coil greater than 2.5 ohms.
75 Tips

Your # 30 answered my question. I have two meters and both show this reading. This 12-volt coil has been on the 8N since 1997 Never a hiccup. Thank you, Tom/Idaho

(quoted from post at 20:15:54 03/08/21) Your # 30 answered my question. I have two meters and both show this reading. This 12-volt coil has been on the 8N since 1997 Never a hiccup. Thank you, Tom/Idaho


<img src="https://www.yesterdaystractors.com/cvphotos/cvphoto80851.jpg">

Click to expand...

The shotgun shells are going to come in handy :shock:

TOH

Put the test leads firmly together and see what reading you get.
75 Tips

Square Coil and Round Coil talk - so we assume you have an 8N? How did you convert from square to round? Get out your Essential Manuals. The FORD front mount distributor uses the 'square coil'. The electrical system also uses the OEM Ballast Resistor. This setup was used from '39 thru '50 then FORD changed to the angle (side) mount distributor that used the 'round coil' and deleted the Ballast Resistor. The 8N, after s/n 263843, used the round can coil and no resistor. It had a passive junction block see diagrams. The OEM FORD electrical system was 6-VOLTS/POSITIVE GROUND. Later, fellas began switching to 12V/NEG GRN eschewing the Generator & Voltage Regulator and adding an alternator. The OEM Ballast Resistor is used on a 12V job as well with front mount system. On 12V, if coil is a 6V unit, you add an in-line 1-OHM Ceramic Resistor in the circuit. You omit the extra resistor by replacing the 6V coil with a 12V coil. Better do some more homework and understand what you are doing so as to not do damage to the system or yourself. By the way, know that YT is NOT a parts manufacturer. They are just a supplier of parts stocked by other suppliers.


FORD 8N TRACTOR WIRING DIAGRAMS:
PRIOR TO S/N 8N-263844:

FORD OEM BALLAST RESISTOR -USED ONLY WITH FRONT MOUNT DISTRIBUTOR:

EXTERNAL 1-OHM CERAMIC RESISTOR - USED ON FRONT MOUNT AND
ONLY IF COIL IS 6V:

*PICTOGRAM courtesy of JMOR

OEM 8N WIRING(6V/POS GRN) AFTER S/N 8N-263844 WITH ANGLE (SIDE) MOUNT DISTRIBUTOR:

FORD 8N TRACTOR ELECTRICAL SYSTEM AFTER S/N 263843 (ANGLE MOUNT):



FORD 8N TRACTOR ESSENTIAL OWNER/OPERATOR/PARTS/SERVICE MANUALS:


Tim Daley(MI)