The Stovebolt Site Forums The Shop Area The Electrical Bay 6 Volt Coil, 12 Volt System?

I have a 1946 Chevrolet Utility, 1958 235 engine, 12 volt system.
I am in the process of attempting to make the 58 engine look like a early 216-235.
It currently has a ballast resistor affixed to the firewall. I would like to be able to use a original 6 volt coil with the main coil wire facing towards the floor, and the electro lock from the dash-key to the top of the 6-v coil.

If I keep the ballast resistor, will that drop the voltage from 12-v to 6-v? I think the ballast resistor is in-place to not burn up the points?

Thank you,

Dale

It'll drop the voltage to around 9 volts but that's on a 12 volt coil. You could measure the voltage at the coil (key on, points closed) using your 6 volt coil to see if it will work or not.

Or, you could use an internally resisted 12 volt coil and eliminate the ballast resistor.

no Dale, you can't use a 6v coil on 12V .... but you can mount the 12V coil up or down

Bill

Use two ballast resistors in series, and see what the voltage is at the coil with the points closed, and/or with the engine running. You might be able to hide one or both of of the resistors somewhere it's not obviously in sight, if you want to have a stock-appearing underhood area.
Jerry

Jerry,

That’s what I’m talking about. I can hide the ballast resistors under the dash, like you say.
See, I am confused as to why when you convert to 12 volt system, they say to use a 12 volt coil, but then you need to use a resistor? I can’t wait to get the engine back together to do your recommended test. Just for grins anyway.

My goal is to make the 1958-235 look as much as a 1946-216 as possible.
Dale

The "12 volt" coil is designed to run most efficiently at about 9 volts, the voltage that's usually available when the battery is under load while running the starter. As the engine begins running and the charging system kicks in, the voltage can go as high as 14.5 volts. To prevent damage to the points due to excessive current flow, the terminal voltage available at the coil during normal running must be dropped to 9 volts or so by using the resistor. During cranking, the resistors are bypassed by connecting battery voltage directly to the coil, either with a separate circuit from the ignition switch, or a bypass circuit from the starter solenoid.

A "6 volt" coil is designed to run at a maximum voltage of 7.5 or so, so if you plan to run that coil on a 12 volt system, you'll need to drop more voltage with resistors before it gets to the coil. DO NOT HIDE THE RESISTORS UNDER THE DASH! Ballast resistors develop heat, and they must be in an area of good ventilation. I'd suggest putting them near the radiator, maybe on the front side of the core support where they're exposed to ram air as it passes through the radiator.
Jerry

Interesting thread. I'm also looking at converting mine to an 3 wire alt.

I have several 12 volt coils laying around (different manufacturers), and so how can I test that any are "internally resisted"?

Also, there's also a spare '83 318 DodgeVan ballast resistor -- think that will work on a conversion if none of the coils are internally resisted?

If the Dodge ballast has 4 terminals, it's got two resistors in it. One is somewhat higher resistance than the other. Use whichever side applies about 9 volts to the coil during normal running. If you're planning to use the 6 volt coil on 12 volts, it might be possible to run the two resistors in series to drop the voltage enough to make the coil safe to use.
Jerry