8N Ford 6Volt to 12 Volt Conversion

[Grabatire]

I'm doing the 6V to 12V conversion on an 8N with front mount distributor and bought a 12 volt coil.

My question is: Does anyone know if the 12V coils have a built in resistor, or do I need to add one? There wasn't any information that came with with the coil.
 

[Dell (WA)]

grabatire..........ALL squarecan ignition coils need the "infamous ballast resistor"........NO ARGUE!!!!

They do NOT have a built-in resistor.

Surprizingly enuff, both the points (0.015") and the condenser work just fine on 12V. Same with the OEM 6V-starter motor. Works fine on 12V, positive or negative ground. .......Dell, a 12V advocate for the right reasons, who knows 8-ways to convert to 12V and they all work right the first time
 

[souNdguy]

keep the oem ballast resistor with the newer 2.5 ohm ( usually ) square coil.
 

[Grabatire]

Thanks soundguy and Dell.

The new 12V coil is a square coil like the original 6V. I was hoping it had a built-in resistor because the oem resistor is toast, but if I read you right soundguy, the oem resistor would do the trick if it was OK?
My neighbour has an early 8N, so I can measure the resistance of its oem resistor and see how it compares to a resistor from a 1980 Dodge truck. I suppose I can run two of them in series if one isn't enough.
 

[Dell (WA)]

grabbatire........NO....NO....NO......the "infamous ballast resistor" is a special kind of resistor that changes value with heat. It starts out about 0.5-ohms and as it heats up (inna'bout 2-mins) it INCREASES in value to about 2-ohms. This is something you can NOT measure with common ohm-meter. But you can measure the effect on the top of your 1-terminal squarecan ignition coil with yer VOLT meter. Ittza LAW, Ohms Law.

The "infamous ballast resistor" is like yer lightbulb, it either works or it don't. So iff'n yer tractor starts, guess what??? Yer ballast resistor is working. .........Dell, yer self-appointed sparkie-meister
 

[Grabatire]

OK guys, I'll try to find an oem resistor. The owner of this tractor had put a jumper across the terminals of the resistor when it burned out so he could feed his critters, but the points didn't like it and eventually gave up. That's when he asked me to convert it to 12V. I've worked on the engines of these little tractors quite a bit, but never did a 12V conversion on one.

I guess I should ask; What is the voltage I should be shoot'n for when measured at the terminal on top the coil? It's my understanding that the original 6 volt system was reduced to near 4 volts at the points by the oem resistor. Would that be a bit too much to expect on a 12 volt system.

I found some 12 volt conversion information on the 'net' that showed a second resistor in series with the oem resistor but it didn't say whether the coil was still 6V or had been changed to 12V.
 

[souNdguy]

the oe resistor is commonly available.. get it. otherwise you will be playing hide and go seek matching up a fixed ressitor value.

new 2.5 ohm coil and old oe resistor tend to play well together.

soundguy
 

[JMOR]

[Dell (WA)]

grabatire.........many times, instead of replacing the burned points, shadetree mechanics will "jump" the ballast resistor for hotter sparkies and eazier starting. Unfortunately, they fergitt to remove the jumper and MELT the insulative tar inside the squarecan coil and will no longer start 'cuz you end up with weak sparkies and BAD coil.

Heres the deal on extra resistor. Many "bubba" conversions are done on the "cheap". Use the original ballast resistor plus a 12V-to-6V conversion resistor in series like flashlite batterys. (resistors are cheaper than new 12V coil)

As fer voltage readings, about 4-volts at top of the 6V squarecan coil and about 10-volts at top of new 12V squarecan coil (with the points CLOSED) .........Dell, yer self-appointed sparkie-meister
 

[Mimos]

Where can I find the manual that has Ittza LAW Ohms chart ?
 

[JMOR]