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Grilles for 1934, 35, and 36 GM trucks


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#633128 - Mon Mar 29 2010 09:31 AM 6 Volt Coil, 12 Volt System?
46Canopy Offline
Wrench Fetcher
Registered: Fri May 02 2008 09:08 AM
Posts: 206
Loc: Los Angeles CA
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
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#633177 - Mon Mar 29 2010 12:30 PM Re: 6 Volt Coil, 12 Volt System? [Re: 46Canopy]
waldo53 Offline
Shop Shark
Registered: Sat Dec 09 2006 12:00 PM
Posts: 1707
Loc: ID
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.
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#633184 - Mon Mar 29 2010 01:25 PM Re: 6 Volt Coil, 12 Volt System? [Re: waldo53]
squeeze Offline
Master Gabster
Registered: Sun Jul 08 2001 12:00 PM
Posts: 5814
Loc: Vancouver Island
no Dale, you can't use a 6v coil on 12V .... but you can mount the 12V coil up or down

Bill
_________________________
"When we tug a single thing in nature we find it attached to the rest of the world" John Muir
"When we tug a single thing on an old truck, we find it falls off" me
Some TF series details & TF heater pics & Rust-a-holics Unanimous parking lot
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#633189 - Mon Mar 29 2010 02:39 PM Re: 6 Volt Coil, 12 Volt System? [Re: 46Canopy]
Hotrod Lincoln Offline
Extreme Gabster
Registered: Mon Feb 23 2004 12:00 PM
Posts: 11207
Loc: Dellrose, TN
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
_________________________
My best friends are Sam, Eli, Bill, and Gene:
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#633245 - Mon Mar 29 2010 06:19 PM Re: 6 Volt Coil, 12 Volt System? [Re: Hotrod Lincoln]
46Canopy Offline
Wrench Fetcher
Registered: Fri May 02 2008 09:08 AM
Posts: 206
Loc: Los Angeles CA
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#633361 - Mon Mar 29 2010 10:42 PM Re: 6 Volt Coil, 12 Volt System? [Re: 46Canopy]
Hotrod Lincoln Offline
Extreme Gabster
Registered: Mon Feb 23 2004 12:00 PM
Posts: 11207
Loc: Dellrose, TN
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


Edited by Hotrod Lincoln (Mon Mar 29 2010 10:45 PM)
_________________________
My best friends are Sam, Eli, Bill, and Gene:
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Eugene Stoner

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#634351 - Fri Apr 02 2010 11:56 AM Re: 6 Volt Coil, 12 Volt System? [Re: 46Canopy]
55firstseries Offline
New Guy
Registered: Tue Nov 14 2006 12:00 PM
Posts: 19
Loc: Victoria, B.C.
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?
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#634481 - Fri Apr 02 2010 09:30 PM Re: 6 Volt Coil, 12 Volt System? [Re: 55firstseries]
Hotrod Lincoln Offline
Extreme Gabster
Registered: Mon Feb 23 2004 12:00 PM
Posts: 11207
Loc: Dellrose, TN
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
_________________________
My best friends are Sam, Eli, Bill, and Gene:
Samuel Colt
Eliphalet Remington
Bill Ruger
Eugene Stoner

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