8N Resistor Question (6V to 12V conversion)

fordstick

New User
I was performing a 6V to 12V conversion on my 1948 8n (front mount coil and distrubutor) when I noticed that my original resistor was completely missing. The block is still there and terminal posts are still there but no resistor. Can I just attach the 2X 1-Ohm, 10W resistors between the posts where the old resistor is supposed to be?
 
(quoted from post at 21:57:05 07/14/20) I was performing a 6V to 12V conversion on my 1948 8n (front mount coil and distrubutor) when I noticed that my original resistor was completely missing. The block is still there and terminal posts are still there but no resistor. Can I just attach the 2X 1-Ohm, 10W resistors between the posts where the old resistor is supposed to be?
Ohms is far too big. Get the right part and save grief.
 
I believe he's referring to Dell's method of reducing voltage to the coil using fixed value resistors. He used two Radio Shack #271-131 ceramic resistors, twisted together, to create a 1/2 ohm 20 watt resistor. This gives a good hot spark and lowers the ignition voltage sufficiently to protect the 12V square can coil. No other resistors are needed. But you will need to mount them on something like a micarta block to insulate them from the frame. I used this method on my 48 8N, still running great after more than 2 years. Search this forum for "Radio Shack 271-131" and you will find more info.
 
Sorry, that search returns too many results. Search for posts authored by me, and read the one entitled "Thanks for help with 48 8N". The original information provided by Dell can probably be found but may take a while.
 
Yes, I was referring to Dell's method. I just wasn't sure if I could bridge the missing resistor or if I was supposed to install it in series with the coil wire, but I guess this is basically the same thing. Thanks.
 

"infamous ballast resistor"

I set out to research the magic about this around 2005/6 with the help of great minds here its a basic calculation Ohms law whoda thunk it...

"infamous ballast resistor" somethings just stick in your gourd...
 
The OEM ballast resistor is .3 ohms cold and 1.7 ohms hot.....very hot.

In other words, it changes value as it heats up. At .3 ohms cold, you get max current at start up. As the resistor heats up, it reduces current to less than 4
amps to keep that square 6v coil from melting.

The 2 10w resistor trick will NOT replace the oem ballast resistor. Use that AND the oem ballast resistor if you insist on using a 6v coil on your 12v
conversion. Rather than deal w/ the math and extra wiring for the resistor, most folks just use a 12v coil. BUT, 6v or 12v front coil......still requires the oem
ballast resistor. A 2-pack of 1.0 ohm, 10 watt square power resistors, when connected side-by-side in parallel by twisting their leads together, create a 0.5 ohm, 20 watt squarecan 6 volt coil current limiting resistor.

Do not remove or bypass the OEM ballast resistor.

The result? 1 ohm ballast resistor, .5 ohm R/S resistors, 2.6 ohm coil, 4.1 ohms divided into 14.5 volts gets you 3.5 amps. You're good to go.
75 Tips
 
(quoted from post at 08:09:09 07/15/20) Sorry, that search returns too many results. Search for posts authored by me, and read the one entitled "Thanks for help with 48 8N". The original information provided by Dell can probably be found but may take a while.

Slim, I read that topic and was wondering if I can modify your setup for a 1 wire alternator? If so, do you have any tips? My conversion kit did come with a 12V square coil and a 1 wire alternator.
 

You need resistance across coil to be in the 3.5-4 ohm to prevent frying the points or coil. I reused the 6 volt coil, but had to add 3 of the std resistors in series to get 3.8 ohms. Finally lost the 47 year old coil from the 1974 12 volt conversion and replaced it with a 12 volt coil that does not require an external resistor.
 
(quoted from post at 07:49:11 07/15/20)
(quoted from post at 08:09:09 07/15/20) Sorry, that search returns too many results. Search for posts authored by me, and read the one entitled "Thanks for help with 48 8N". The original information provided by Dell can probably be found but may take a while.

Slim, I read that topic and was wondering if I can modify your setup for a 1 wire alternator? If so, do you have any tips? My conversion kit did come with a 12V square coil and a 1 wire alternator.

my hack for a 1 wire alternator was to use a DPST switch.

DPST-toggle-switch.png


wired both poles together, and to the battery + terminal. one throw goes to the alternator, the other throw to the ignition, so when you flip the switch off both the ignition and alternator are disconnected.
 
Get your ESSENTIAL MANUALS and learn how it is supposed to be wired as OEM 6V/POS GRN then how it a 12V is correctly installed, then can convert if you insist.

FORD OEM BALLAST RESISTOR -USED ONLY WITH FRONT MOUNT DISTRIBUTOR:
swlv82hh.jpg
FIK0D4Ih.jpg

HELP: The LH resistor Terminal Post connects to the COIL Stud Terminal Post as you face the back off dash. OEM Wiring is RED.


EXTERNAL 1-OHM CERAMIC RESISTOR - USED ON FRONT MOUNT AND
ONLY IF COIL IS 6V:
XRLi3vSh.jpg

FRONT MT 12V:
noSTej6h.jpg


*PICTOGRAM courtesy of JMOR


FORD 8N TRACTOR ESSENTIAL OWNER/OPERATOR/PARTS/SERVICE MANUALS:
qI9P22kh.jpg





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