6 volt coil
Lead Driver
Joined: Apr 2002
Posts: 8,813
Likes: 13
From: Littleton, New Hampshire
Originally Posted by 48ATOY
on a stock 6 volt ing.
is there a voltage reducing resistor on the system
I have to replace my coil spark jumping cracked top
on some 12v you need a resistor?
Joe
is there a voltage reducing resistor on the system
I have to replace my coil spark jumping cracked top
on some 12v you need a resistor?
Joe
Elder User
Joined: Dec 2003
Posts: 531
Likes: 1
From: New Mexico
So why is it that there needs to be a difference between 6V and 12V coils? If a coil does the same thing to voltage, why does the input matter? Shouldn't there just be one coil and 6 volts input does what it does and 12 volts does what it needs to?
Questions of life I often ponder
Questions of life I often ponder
Lead Driver
Joined: Apr 2002
Posts: 8,813
Likes: 13
From: Littleton, New Hampshire
Originally Posted by dffay
So why is it that there needs to be a difference between 6V and 12V coils? If a coil does the same thing to voltage, why does the input matter? Shouldn't there just be one coil and 6 volts input does what it does and 12 volts does what it needs to?
Questions of life I often ponder
Questions of life I often ponder
Elder User
Joined: Dec 2003
Posts: 531
Likes: 1
From: New Mexico
Thanks, but its not a regular appliance that is supposed to do from a certain voltage input and only that work. A transformer is a linear arrangement that steps up, so if a 12volt coil were only fed 6 volts, its should act like a 6 volt coil--step up transformer--shouldn't it?
Posting Guru
Joined: Jun 1999
Posts: 2,415
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From: Comox Valley, Canada
Originally Posted by dffay
Thanks, but its not a regular appliance that is supposed to do from a certain voltage input and only that work. A transformer is a linear arrangement that steps up, so if a 12volt coil were only fed 6 volts, its should act like a 6 volt coil--step up transformer--shouldn't it?
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Lead Driver
Joined: Apr 2002
Posts: 8,813
Likes: 13
From: Littleton, New Hampshire
My only experience with this was many years ago when I converted a 6V system to a 12V on a 34 Plymouth. I forgot about changing the coil and it worked fine for about a week before it burned up... 
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Brett Foote
Senior User
Joined: Oct 2006
Posts: 299
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From: Topeka, KS
Extensive idiot training has taught me that you CANNOT afford to let the magic smoke escape from any electrical components... That's BAD...
I'll admit I've forgotten more than I know about all this, but I was of the understanding that the voltage drop let the points last longer as well.
I'll admit I've forgotten more than I know about all this, but I was of the understanding that the voltage drop let the points last longer as well.
Fleet Owner
Joined: Jul 2004
Posts: 27,299
Likes: 1,059
From: NM
Essentially they did the same thing with coils that they did with the gauges, when they went from 6v to 12v. Instead of a CVR like on the gauges, they used a ballast resistor, which is not a linear resistor. They are nichrome-wound filaments and the resistance changes with temperature. At idle the ballast gets hotter and has higher resistance, which is OK because the engine needs less spark and it keeps the coil cool and maximizes point life. That is also why they bypass the ballast on Ford 12v starter solenoids, it would otherwise be getting a weak spark. At higher speeds the ballast runs cooler and its resistance is somewhat less, and gives a hotter spark which the engine needs because it has higher compression pressures (higher cyinder fill).
The Ford cars with 6v systems actually had ballast resistors in the late 40's. I've never figured out why.
The Ford cars with 6v systems actually had ballast resistors in the late 40's. I've never figured out why.
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