smta coil

There is a resistor block between the 12 volt power source and coil reducing the voltage to 6volts I checked this with a meter.My question is this a 6 volt coil? Can I elimate the resistor block and run 12 volts thru the existing coil or do I need to up grade to a 12 volt coil,to the best of my knowelge this tractor came from the factory with the option of a 12 volt system.I am running a petronix pointless ingition and autolite 388 plugs gaped at .032 but the color reading after 1 year of use indicates not enough fire in the wire,this tractor is used very little and not worked hard.Any input thanks.Paul

twelve volts for a ih gas tractor didn't come until midway thru 450 production. you should have bought the pertronixs hot coil also and run 3116 plugs at .040.

Lets take your questions one at a time:

QUESTION 1 My question is this a 6 volt coil?

ANSWER: If it has a Ballast resistor ahead of it NORMALLY that would mean YES its a 6 volt coil BUTTTTTTTTT I cant guarantee that from sitting here. Cant tell what some farmer did before ???????

HOWEVER there is a way to determine if its a 6 volt coil by measuring the low voltage primary resistance between its lil + and - terminals.

If its around 1.25 to under 2 ohms ITS A 6 VOLT COIL and requires the ballast...............
If its around 2.5 to 3.5 ohms ITS A 12 VOLT COIL and no ballast should be used UNLESS the Pertronix switch requires it for current limiting purposes !!!!!!!!!!!!


QUESTION 2 Can I elimate the resistor block and run 12 volts thru the existing coil or do I need to up grade to a 12 volt coil

ANSWER 2 NO if its a 6 volt coil YOU NEED THE BALLAST ORRRRRRRRR you can upgrade to a full true 12 volt coil AND NO BALLAST IS REQUIRED UNLESS PERTRONIX REQUIRES IT TO LIMIT THE ELEC SWITCH MODULE CURRENT CHEck with them.

NOTE to get the full bang for the buck and utilize all the advantages of an elec switch I would buy a matched (within current limits of the elec switch) high voltage high energy coil and run a wider plug gap.

Got it?? anymore questions??

John T

I do understand ohms law will check at a later date thank you for the information.
As far as Randy Hall's comment,the 12 volt system was an option on the smta from the factory according to the older than dirt service manager at the local IH CASE dealer and has even dug out old parts references to for me to ponder and I really dont belive it my self but black and white is just that.It was an option.Paul

you can believe what you want. the diesel's were twelve volt the others were six. a lot of options on my original super mta dealer price sheet but no twelve volt for gas tractors.

Also being one of them older than dirt guys, I would like to see the 12 volt option in black and white, for a gasoline smta, and like John said, use the ohm meter to see if you have a 12 or 6 volt coil, I have run into conversions where people put on a 12 volt coil and also the ballast resistor, which results in low coil output.

You can eliminate the resistor block IF you use a 12 volt coil with INTERNAL resistor.