[AT] tractor electrical question

[deanvp at att.net]

I am not familiar with the I/H Farmall tractors electrical set up but on JD’s 20 and 30 series JD Two Cylinders, 1956 to 1960, JD inserted a dropping resistor that was bypassed during starting to give a full 12 V to the points and then when the starter was released it dropped back to 6 V to extend point life.  But when things don’t make sense it usually comes down to a bad connection somewhere.  Starting with grounds.                                                                                                                                                                                                                                            

 

Dean VP

Snohomish, WA 98290

"Socialism is a philosophy of failure, the creed of ignorance, and gospel of envy, its inherent virtue is the equal sharing of misery."

..Winston Churchill...

 

From: AT <at-bounces at lists.antique-tractor.com> On Behalf Of John Hall
Sent: Wednesday, August 25, 2021 9:01 PM
To: at at lists.antique-tractor.com
Subject: Re: [AT] tractor electrical question

 

There is a wire tied in from the starter solenoid also. You would assume a new OEM coil to be good but who knows. All I know is it acts the same with both coils. I will note that the new coil had to be rotated 180 in the bracket to get it to hook up. The power is going in the plus side, just like schematic shows. Maybe they just put it in wrong at factory?

John

On 8/25/2021 11:52 PM, Jason wrote:

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 <mailto: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 <mailto: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 <mailto: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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