12 volt ignition coil

S

Steve Rinaldo

Member
I have heard that using a 12 volt ignition coil with out a resistor for a points ignition is Ok to use on a 6 volt system. Thoughts or experience?
 
I've done that w/out problems, best is to check the primary resistance of the coil, should be aprox 1.5 ohms.
 
My opinion.


If it is a true 12v coil with 3 ohm primary, it will probably work. However the spark may not be as strong, and if wear/deposits occur may cause the motor to run poorly and combustion may not be as efficient.


If running a 6v ignition system, best to run what it was designed for with a 1.5 ohm coil primary
 
Lots of experience.
It depends on the resistance, 3 ohm is fine. 1.5 ohm is not.
Install the coil, turn it on with points open, measure voltage. Anything over 8 volts will burn the points quickly. So, if you get an over-voltage install the resister.
Its probably best to just get a 1.5 ohm epoxy filled coil.




The Pertronix epoxy filled coil will work nicely and looks fine. 6v, 1.5 ohm part# 40111. 12v, 3 ohm, part# 40611. I think I have the part #'s correct, the info would be on their website.
 
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Patrick L. said:
Lots of experience.
It depends on the resistance, 3 ohm is fine. 1.5 ohm is not.
Install the coil, turn it on with points open, measure voltage. Anything over 8 volts will burn the points quickly. So, if you get an over-voltage install the resister.
Its probably best to just get a 1.5 ohm epoxy filled coil.




The Pertronix epoxy filled coil will work nicely and looks fine. 6v, 1.5 ohm part# 40111. 12v, 3 ohm, part# 40611. I think I have the part #'s correct, the info would be on their website.
Click to expand...


Umm - He is asking about putting a 12 V coil on a 6 V system, therefore he should use a 6v 1.5 ohm coil.


If he uses a 12v 3 ohm coil on 6v he will have less current in the coil. have a weaker spark. I do not think that will burn the points or damage teh coil?


Or perhaps I do not read the response correctly.
 
Seems to me I recommended a 1.5 ohm coil preferably epoxy filled, but, that is not what was asked. So he can either change the coil which he doesn't appear to want to do or he can check voltage to the points or ohm check the coil.
 
When 12V systems came out in the mid 1950s, ignition coils remained the same for 6v systems, but external resistance was added. When starting the car, the add-on resistance was bypassed to give the coil a 12V boost. Once the engine started and the ignition key went into the run position, the extra resistance was cut-in so the coil ran on 8v.
 
i was told that a 12v coil is ok on 6v , but on 12v it needs the resistor ..
FSI ignition on mine . 12v with resistor
 
Actually , a six volt 1.5 OHM coil can be used on 12 volts if a resister is used . The resister prevents the full 12 volts from entering and burning out the 6 volt coil . In other words a three OHM coil can be used on 12 volts without a resister . If a 1.5 Ohm coil and resister is used on 12 volts the ignition will still be running 6 volts , The starter and lights will get 12 volts .
 
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