[Farmall] Need Expert Opinion

[szabelsk at gdls.com]

The H died last weekend and I traced the problem to the coil apparently 
having an internal short. Had no spark at the plugs, and the coil was warm 
while the ignition switch was on, and something was draining the battery.

The PO had converted the H over to a 12V system. Figured I go get a new 6V 
coil and change the condenser and points while I was at it. After removing 
the coil I noticed it was marked 12V, not 6V. Also, the resistor that 
should be in line with the coil was actually in parallel with it. Don't 
know what value it is supposed to be since it was broken and I believe the 
one end should have been grounded, but wasn't. This is probably what fried 
the coil since it should have seen twice the current.

I believe the entire resistor is there, it's just broken near the one lead 
that was supposed to be connected to ground. Measured what was there and 
got about 1.2 ohms. I figure the PO was using this resistor to cut the 
current in half at the 12V coil (wired from ignition switch to one end of 
the resistor, same end of the resistor wired to "+" on the coil). Maybe 
the PO also swapped out the points and condenser with 12V pieces to make 
the whole thing a 12V system(???).

Anyway, since I was going to replace the points and condenser with 
standard 6V parts, I figured I'd just use a 6V coil with the resistor in 
series to drop the voltage down. Went to NAPA and picked up a 1.20 ohm 
resistor (ICR13), a 6V coil (IC7) and a tune up kit for the ignition 
system. When I got home I noticed that the coil is marked "NO EXTERNAL 
RESISTOR REQUIRED". I measured the coil resistance and read about 1.3 
ohms.

Now I know that the resistor is needed to drop the 12V down to 6V, by in 
essence making the total circuit resistance twice what the coil resistance 
is (somewhere between 2.4 to 3. 5 ohms total) and dropping 6V across the 
resistor.

My question is, with the  "NO EXTERNAL RESISTOR REQUIRED" marking on the 
coil, should I still use the resistor? If I don't, then I'll be putting 
12V to the coil, and the total resistance will only be somewhere in the 
area of 1.3 ohms. Probably burn the coil out real fast.

If I put the resistor in, I'll drop the voltage to 6V and have the 
required 2.4 to 3.5 ohms total. But what does the  "NO EXTERNAL RESISTOR 
REQUIRED" now mean?

Is this marking there because this coil has other applications that would 
allow eliminating the in line resistor, and should I just ignore it?

I did ask the guys at NAPA about this and they said I didn't need the in 
line resistor, but I don't know. I'm going to call another local NAPA 
store and see what they say about this.

Anyway, I really appreciate any and all input from anybody on this list.



Carl Szabelski



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