Ballast resistor for coil?

[vegas paul]

I am converting from 6V pos. ground to 12V neg. ground and also adding an electronic ignition distributor from Dave Thibault. The 12V coil I purchased from Randy Rundle has an internal resistor, and warns that any external ballast resistor must be removed.

Question: I can't find an external resistor in my car or on the wiring diagram. Was this contained within the harness? Or did the original 6V coil not require this?

Dave's electronic ignition states that the ballast resistor must be used, or included in the coil (but not both!). I don't want to fry this expensive piece of equipment, so please offer any advice.

Las Vegas, NV
'51 Champion Business Coupe G899965 10G-Q4-1434

[StudeRich]

Paul; 6V cars do not have or need a resister, that would only be on 12V cars to allow them to run on 8-10 volts after starting on 12 volts. Your car should not have one and you should be good to go with the coil only, if that is the OHM rating coil that Dave T recommends!

quote:Originally posted by vegas paul


Question: I can't find an external resistor in my car or on the wiring diagram. Was this contained within the harness? Or did the original 6V coil not require this?

StudeRich
Studebakers Northwest
Ferndale, WA

[vegas paul]

Thanks... looking for that resistor was driving me nuts!

Las Vegas, NV
'51 Champion Business Coupe G899965 10G-Q4-1434

[curt]

I just put a 12 coil with an internal resistor on my 1955 car, it is a 12 volt conversion. I have been told the points, in the distributor, will burn fast if the coil operates on 12 volts. Some cars without an external resistor used a pink resistance-wire from the ing. switch to the coil, instead of the external resistor. This pink wire statement should be true ONLY on an original 12 volt Stude car. Your 6 volt will not have a pink wire.

[John Kirchhoff]

If memory serves me correctly, in the good old days, 6V coils usually had 4 ohms resistance on the primary winding. Later 12V jobs with the ballast resistor or the resistance wire were usually 2.5 ohms...I've never had reason to measure a Stude resistor, but I wouldn't be surprised if they're around 1.5 ohms. When electronic ignitions came out, most of those coils had 1.5-1.7 ohms resistance. Chryslers used a dual ballast resistor, 1 ohm for starting and 4 for running which gave around 2.5 ohms for starting and 5.5 for running. Average those two out and you have 4 ohms, just like the good old days. Modern distributorless twin lead GM coils have around .9 ohms and some Chrysler jobs have 2.5 ohms.

All this is actually leading somewhere, believe it or not. Modern electronic ignition boxes are picky about coil resistance, so be careful when replacing the coil with another one. I recently put GM coils on my motorcycle and had to add a 1.35 ohm ballast resistor to get a total of 2.25 ohms, right in the middle of factory specs. Get too much resistance and the spark will be so weak your engine will never start and not enough and you can be putting extra current through that high dollar black box. Any coil with too little resistance will work with your ignition AS LONG as you have a ballast resistor that makes up the correct resistance value for your ignition box.