The Stovebolt Site Forums The Shop Area Engine Shop Ignition ballast resistor CONFUSSED!!!!!!

I want to get something figured out here.

I just read a thread on a engine not firing, I notice there was a lot of talk about if a ballast resistor was being used or not.

I have a 12 volt conversion on my truck, with a 12 volt coil, starter and generator. With the 12 volt coil, do I STILL need a ballast resistor in line? Can't the 12 volt coil handle the 12 volts from the ignition switch? If not why even change the coil from the original 6 volt coil?

I just purchased a 12 volt ceramic ignition resistor last weekend from the auto parts store, I thought I could use it on my heater blower motor, decided it wouldn't handle the amperage draw. HONESTLY, I couldn't really see what it did at first. I hooked up my 12 volt power supply with a meter in-line through the resistor it still read 12 volts. Then I put a 12 volt light bulb on it and I saw it was definitely dimmer, must need a small draw of current to work correctly.

What happens when one isn't installed? does it just burn up the points sooner? I am guessing the resistor is installed on the "POSITIVE" side of the coil. Right now my coil hot lead comes from the switch with NO resistor and my truck is "NEGATIVE" grounded. If so, that could explain all the used set of burnt points left in the glove compartment.

Someone please explain this to me in STUPID terms. I'm a machinist, not a electrical engineer.

CONFUSSED JOHN

I'll put it as simple as I think about it - the ign resistor is in line in normal operation cuz the full 12V [or 6 as the case may be] isn't necessary for proper ignition, and will shorten the life of points and, yes, coil - when the motor is cranked, the starter is drawin so much current that the ign may not get quite enuff to fire quickly, so the ign resistor is bypassed - a resistor is used to drop some of the current - if there's no draw [like B4 ya put the lite bulb in] then the resistor doesn't have anything to do - confused?
use an ign resistor - see your years wiring diagram for just where it hooks in

Bill

Huh? Lightbulb? :confused:

Look, unless you're installing HEI that specifically tells you not to, use a ballast resistor. Putting 12 volts to the points will burn them up in short order. I was told that 8 volts delivers as hot a spark as you can use without melting stuff, and the 6v coil is not likely to withstand anything over 6v for long. This, too, may be an urban legend... I chose not to test it.

edit: Newer GM starters have a 12v output that connects to the coil and is only hot when the starter is spinning.

12 volt points igniton coils need around 3.2-4 ohms to give good points life. Some aftermaket coils may have this much resistence built in allready. Using an ohm meter to check between the two small terminals on the coil,most are 1.8 ohms, so you may need a ballast resistor.

Or you can just install a 12 volt coil with an internal ballast resistor.

Am I remembering correctly that a 12v coil actually runs on about 9v? As mentioned above, some coils are not used with a resistor.