[Farmall] Need Expert Opinion

[Darrell Ratliff]

Carl – the fallacy of the information from the NAPA guys is that it is a 6 volt system.  In this case you have to consider yours a 12 volt system because the battery that is supplying energy is 12 volt.  Your components are 6 volt components (coil) and since you are supplying it with a 12 volt battery you will need the external dropping resistor in series with the coil to reduce the effective voltage to the coil.  Even though the coil is marked “no external resistor” it is a 6 volt coil and is designed to operate on that voltage.  Powering it from a 12 volt battery without dropping the input voltage will cause it to fail quickly.

From: szabelsk at gdls.com 
Sent: Thursday, October 27, 2011 12:27 PM
To: Farmall/IHC mailing list 
Subject: Re: [Farmall] Need Expert Opinion

Jim,

That's were I started trying to figure out what was going on with the 
original wiring that was on the H to start with.

The ignition system was wired with a 12V coil (don't know what kind it was 
other than a Delco, and a really rusty one at that) and an external 
resistor that was in "parallel"  with the coil, not in series. The wire 
from the ignition switch went to the resistor on one side, and from that 
same side, then went to the coil (+). The other end of the resistor was 
grounded through it's mounting bracket. The coil (-) went to the 
distributor. 

Now when I went to replace the coil, I knew I needed a resistor in line to 
drop the voltage. I brought a 6V coil and a new resistor to go with it. I 
didn't realize that the old coil on the H was 12V, and didn't realize how 
the old resistor was wired into it until I took it of and was ready to put 
the 6V coil and new resistor in. 

Since the new coil implies that I don't need an external resistor, I'm 
confused as to whether or not I really need it. If I was putting the 6V 
coil on a 6V tractor, I guess I wouldn't worry about it. But this is a 12V 
tractor.

The Guys at NAPA said that the fact that I had a 6V ignition system 
determined that I needed a 6V coil and didn't need the in-line resistor. 
That's where I disagree with them. I don't think putting a 6V coil in a 
12V system without an in-line resistor is a good idea. That also doesn't 
agree with the fact that the H had a 12V coil to start with.

In your response you only mention three coils

---- 6 volt
---- 12 volt, no resistor required
---- 12 volt, resistor required

Are you saying that there is only one kind of 6V coil? Or are there two, 
one with and one without a resistor required? The new one I have says no 
resistor, but that wouldn't have been the case 50-60 yeas ago would it? 
Aren't the coils that don't need a resistor later/newer technology?

Don't mean to contradict you or anything, just want to make sure I 
understand everything and get things wired up right the first time. I 
really need to have the H up and running this weekend.

Carl Szabelski



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