[AT] Ford 8n Under Dash Resistor?

[Ronald L. Cook]

Mike,
	On that Farmall you should be bypassing the resistor when cranking. 
Maybe you have a broken or corroded bypass wire.  I have had that happen 
on an old Chevrolet.
	I tried a little, not to hard, to figure out how to bypass a bad 
resistor on my 2N for starting purposes.  Thought about a relay, but 
just used my pocket knife to pass the current past the resistor.  It 
worked until I got a new resistor from New Holland.

Ron Cook
Salix, IA

Mike Sloane wrote:
> Well, there is another "fly in the ointment": resistance in a wire is 
> also dependent on temperature. If you don't use a heavy enough wire, it 
> will heat up, and the resistance (and the voltage drop) will change. But 
> heavy wires have less resistance than thin ones. Most "ballast" 
> resistors are cast into blocks of "sand" to help stabilize the heat. 
> Here is a lab worksheet addressing the issue: 
> <http://spiff.rit.edu/classes/phys273/manual/temp_coeff.html>.
> 
> So, while Steve's idea would work some of the time, it won't work all of 
> the time. When I install a ballast resistor in a tractor that I am 
> converting from 6 volts to 12 volts, I try to place it in the air stream 
> of the fan in an attempt to keep the temperature change to a minimum.
> 
> In fact, I have a Farmall 340 that I converted (and installed a 
> Pertronix ignition module) not too long ago, and I am having trouble 
> getting it started due to poor spark. Once started, it runs fine, and I 
> am beginning to suspect that the culprit might be the ballast resistor I 
> installed when I did the conversion.
> 
> Mike
> 
> Dudley Rupert wrote:
>> The wire is a good idea, Steve.  If the coil resistance were measured then a
>> piece of wire with a resistance roughly 150% of that of the coil would be a
>> good starting point.  The objective here is to get a voltage drop across the
>> wire of 5 volts.  If the drop is greater than 5 volts then shorten the wire
>> and if it is less than 5 then lengthen it.  If a guy had a low ohm wire
>> wound potentiometer (variable resister) that might be fun to try too -
>>
>> Dudley
>> Snohomish, Washington
>>
>> -----Original Message-----
>> From: at-bounces at lists.antique-tractor.com
>> [mailto:at-bounces at lists.antique-tractor.com]On Behalf Of Stephen Offiler
>> Sent: Wednesday, January 07, 2009 5:14 AM
>> To: Antique tractor email discussion group
>> Subject: Re: [AT] Ford 8n Under Dash Resistor?
>>
>> 3 volt coil... that's news to me, too.  Thanks Mike.
>>
>> If originality is not a goal, but reliability is, you can sometimes
>> replicate the function of a wirewound resistor with a coil of regular
>> wire.  Depending on the resistance value needed, it might or might not
>> be practical.  Of course, the gage and length of the wire are two
>> critical variables and some math needs to be done to get it right.
>>
>> Steve O.