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Thread: 6V Coil Primary Circuit

  1. #1
    Champion Member lworden's Avatar
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    6V Coil Primary Circuit

    I have three 6v coils for my two 1955 Studebakers. On all three, the primary resistance is 3.5 to 3.8 OHMS. From what I have read , the 6v coil resistance from the (+) to (-) poles should be 1.5 OHM and 3.5 OHM for 12v coils.
    One of them is new from NAPA and says, 6v "no external resistor required."

    Is it all right to use a 6v coil with 3.5 OHMS across primary Circuit??
    Do I need to get an original one from Studebaker NW????
    What damage can this cause?
    Thanks
    Larry

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    Either 6 or 12 volt coils should show roughly 1.5? resistance in the primary windings. A 12 volt coil with an internal resister will show 3.0-3.5?.
    I don't know what you have for a tester, but it has to be a pretty good one to read accurately in the lowest range. Hold the two leads together and see if the meter will zero.

    My Ohms (Omega) symbols showed up as question marks for some reason.
    Last edited by Dwain G.; 05-24-2013 at 06:23 PM. Reason: WTF!
    [SIGPIC][/SIGPIC]

  3. #3
    Champion Member lworden's Avatar
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    Thanks for the reply. My meter reads 4.9 to 5 OHMS when the two leads are put together, not close to zero. Conclusion, meter isn't accurate enough to read the 1.5 OHMS. Thanks again, I'm trying to fix something that isn't broken. There are many other things to fix.

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    Most 6 volt coils have a primary resistance somewhere between 1 and 1.2 ohms and 12 volt coils have a nominal resistance of 1.5 ohms when used with a ballast resistor and around 3 ohms with an internal resistor. I use a vacuum tube voltmeter to check coil resistance because they can be set to show a zero reading when the leads are touched together. Many of the late 30's and mid 40's Fords used an external resistor with their 6 volt coils. Bud

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