[AT] tractor electrical question

[Jason]

Generally most coils have a resistor before them to lower the voltage so
they don't burn up the points. Some applications have a booster wire from
the small  terminal on the starter solenoid. Since there is a voltage drop
when cranking, this booster wire temporarily raises the voltage to help
during starting.

If everything else is fine. A coil that fails as it warms up is a coil
getting close, to well, failing.

Jason

On Wed, Aug 25, 2021, 10:22 PM Howard Pletcher <hrpletch at gmail.com> wrote:

> Is that the original coil?
>
> I'm not familiar with the 454, but in the truck world, most coils are
> intended for 6V use.  There is a resistor wire in the harness that drops
> the voltage while the current is flowing with the points closed.  But there
> are also coils intended for 12V use with no resistor wire.  If that is not
> the original coil, perhaps you have the wrong one.
>
> Since it seems to work fine with 12V applied, I'd probably run another
> wire from the ignition switch to the coil to bypass any possible resistor
> wire.
>
> Howard
>
> On Wed, Aug 25, 2021 at 11:08 PM John Hall <jtchall at nc.rr.com> wrote:
>
>>
>> If there is, I can't find it. Closes thing I have found is the
>> diode/rectifier for the alternator. Its inline and is tied in on this
>> particular "circuit" . Matter of fact, the side opposite the alternator
>> is where the fuel solenoid feeds from.
>>
>> John Hall
>>
>>
>> On 8/25/2021 11:05 PM, Spencer Yost wrote:
>> > Maybe there’s an external resistor?
>> >
>> > Spencer
>> >
>> > Sent from my iPhone
>> >
>> >> On Aug 25, 2021, at 10:35 PM, John Hall <jtchall at nc.rr.com> wrote:
>> >>
>> >> Got what I hope is a simple question. On my IH 454 tractor, is the
>> voltage going to the coil a constant 12V? I'm having some issues with it
>> running bad when it gets hot (I've already replaced everything but the plug
>> wires). Found out today that if I run a jumper wire from battery to the
>> coil, the problem goes away. Take it off problem comes back, put it back it
>> goes away, take it off, it comes back. So I am tracing the wiring but this
>> one isn't simple, new enough there are tons of gauges, fuel solenoids,
>> safety switches, etc. Anyway, if I check voltage at the coil, the fuel
>> solenoid, and there is one small terminal on starter solenoid that all read
>> 12V if the switch is on. If I bump the engine over slightly (I guess the
>> pts are closing) then the coil and starter drop to just under 6V, fuel
>> solenoid stays the same. So shouldn't there always be 12V at the coil?
>> >>
>> >> John Hall
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>
>
> --
> Howard
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