Re: 12 volt coil help

Posted by John T on July 19, 2019 at 06:21:02 from (45.16.200.171):

In Reply to: 12 volt coil help posted by jm. on July 18, 2019 at 17:54:02:

Good morning jm, to add to my post below heres yet more info. I just cant say from here if your truck had originally or was modified to a full true 12 volt coil (NO Ballast required) orrrrrrrrr it uses a 6 volt coil in series with a voltage dropping (12 down to 6) ballast resistor ??????????? You need to determine that if you're going to replace the coil. Also the ballast could be in the form of a resistive wire (may be hard for a rookie to identify) or a stand alone discrete unit like some cars and tractors used.

NOTE Anytime I went to get parts for an older IHC there were always questions of the serial numbers and codes or engine numbers and date of manufacture on and on and on lol. IHC was notorious for lots of modifications and changes even in the same model year grrrrrrrrrrrrrr it was always hard to get the right parts and know what was used... Even more reason NOT to know sitting here what ignition components you may have ????????????

THIS INFO CAN HELP DETERMINE WHAT YOU HAVE:

1) Ifffffffffff it has a ballast resistor (wire or stand alone unit) in series with the coil feed and its intact and works, if you turn on the ignition and good points are closed and all is correct and working THE VOLTAGE ON THE COILS INPUT would read around 6 volts (maybe 5 to 7 subject to ballast and battery and resistances) as that's the nominal operating voltage for a 6 volt coil.

2) Iffffffffffff you turn on the ignition points closed yet there's still close to battery voltage on the coils input, theres obviously no series V = I x R VOLTAGE DROPPING BALLAST. If your system is delivering 12 battery volts to the coil with ign on YOU NEED A FULL TRUE 12 VOLT COIL. If you used a 6 volt coil and applied 12 volts (IE no series voltage dropping ballast) the coil will overheat and the points burn prematurely.

3) Many vehicles that were 12 volt but used a 6 volt coil plus a ballast utilized a ballast by pass circuit ONLY WHEN CRANKING. That might be in the form of an extra I terminal on a starter solenoid (hot ONLY when cranking) or extra contacts on some saddle mount mechanical starter switches or other such devices. ONLY when cranking the ballast being by passed helped cold weather starting by momentarily applying more voltage to the coil. Then when running the series ballast was back in the circuit dropping around 6 volts so a 6 volt coil didn't overheat GOOD SYSTEM

Soooooooooooooo be sure and use the correct coil be it a 6 or a 12 volt. Again if your truck is supplying unballasted battery voltage to the coil under operation (IE no series voltage dropping ballast) YOU NEED A FULL TRUE 12 VOLT COIL NO BALLAST REQUIRED. HOWEVER if it has a working intact series voltage dropping ballast and delivers only 6 volts to the coil YOU NEED A 6 VOLT COIL WELL DUH LOL

NOTE in years of farming plus a used tractor dealer of the hundreds of old tractor coils I saw that were "12 Volts" or "12 Volts not for use with ballast" they had a LV primary (from + to -) resistance in the 2.5 to 4 ohms range and did not have any stand alone internal traditional "resistor" tucked away inside the can. Their 2.5 to 4 ohms resistance was comprised of the wire and coil windings alone IE no coil windings PLUS a separate internal "resistor", although a few older vehicles utilized such a coil that did have a separate "resistor" inside the can. I just never noticed those type of coils with a separate "resistor" inside the coil can on older farm tractors BUT HEY I OBVIOUSLY DIDNT SEE ALL THE OLD TRACTORS OUT THERE so maybe some used those coils ?????????? HOWEVER That may or may not be true for old IHC trucks I CANT SAY FROM HERE WHAT YOU HAVE !!!!!!!!!!!!!!!!!!!!

This may be more info then you asked or needed lol but hopefully it helps you understand and can figure out and buy a correct coil.

Post back any question

John T

Replies:

• Re: 12 volt coil help jm. 19:00:08 07/19/19 (0)

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