Wiring

[mac15b]

So I just got an alternator kit for our 52 8N. Now we are in need of some guidance on wiring this thing up. The diagram that came with the
kit leaves a little to be desired, as the harness doesn't 100% match the diagram. Plus, I didn't think about this, but we have a coil with an
internal resistor, so I'm assuming we don't need the ceramic resistor, so that adds a wrinkle to our diagram. Any suggestions, diagrams?

 

[Bruce (VA)]

Google wiring diagrams JMOR and find the one that fits your tractor.


No modern automotive coil has an internal resistor. Internal coil resistance is determined by wire gauge and the number of turns. Higher resistance is provided by smaller gauge wire with greater turns. If the coil is marked or sold with a notice requires an external resistor that simply means it has a low internal resistance and will be damaged by excessive voltage. It does not mean the coil has an internal resistor. Yes, plenty of coils are advertised as having an internal resistor. Thats called advertising, not electrical engineering. To be both accurate and precise, every automotive coil should simply state the internal resistance of the coil. But that would require a basic understanding of the Kettering Ignition system. So to keep it simple, ANY side coil with an internal resistance of 3.25 ohms will work fine on your 12 volt 8N w/o any external resistor. Like the NAPA coil, p/n IC14SB. Many folks just add a 12 volt coil rather than dealing with trying to find an external resistor to work with their existing 6v coil. Too much resistance gets you a weak spark; not enough and the coil melts.
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[mac15b]

Thank you for that... I know just enough about electricity to be dangerous (to myself!). I had no idea. So am I correct that I don't need the ceramic resistor? If not, do I bypass wiring from the resistor and go direct to the coil?

 

[Bruce (VA)]

If the coil has 3.25 ohms of resistance, no resistor is needed.

Do not bypass it. Remove it.
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