[AT] tractor electrical question

[John Hall]

Howard, you are leaning toward new coil and old coil are both bad?

John Hall

On 8/26/2021 3:47 PM, Howard Pletcher wrote:
> No, what he is reporting is just what should be happening.  With the 
> points open, no current is flowing through the primary circuit and 
> there is 12V at the + side of the coil.  When he bumped the starter 
> and closed the points, the current flowing through the resistor in the 
> primary circuit results in a voltage drop so that there is now 6V on 
> the coil as intended.
>
> The wire from the starter to the coil does send 12V directly to the 
> coil, but this is only engaged while the starter is cranking in order 
> to produce a hotter spark for starting and is not connected to 12V  
> the rest of the time.
>
> The fact the coil seems to require 12V to its terminal when hot points 
> to an internal problem in the coil as discussed by Dell in the 
> Yesterday's Tractors article.
>
> Howard
>
>
>
> On Thu, Aug 26, 2021 at 2:53 PM Carl Szabelski 
> <c.s.szabelski at gmail.com <mailto:c.s.szabelski at gmail.com>> wrote:
>
>      By the way, I believe it’s not the coil and is related to the
>     cranking motor. Especially since the voltage drops when you bump
>     it like you said. Something in the motor may be partially shorted
>     or corroded, causing a voltage drop to the coil. The coil should
>     always see 12V whether or not there is a resistor, internal or
>     external. The resistor is essentially after the coil winding and
>     drops the voltage after the winding, not before it. If the engine
>     is running fine when you directly connect 12V to the coil, the
>     coil is working like it should and is good.
>
>     Carl
>
>
>
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