Topic: Ignition System Resistor


carcrazy    -- 01-19-2010 @ 10:58 AM
  I am using a standard 1937 distributor with a coil adapter kit to allow use of a remotely mounted late model 12 volt coil (B6A-12029-B) in a vehicle which will have a 12 volt negative ground electrical system. The coil has a note on it stating that a resistor should be used but doesn't state what the resistance value should be.
My questions are: What should the value of the resistance be in the primary circuit between the ignition switch and the coil? Which of the coil primary terminals (+ or -) should be connected to the distributor in light of the polarity change of the vehicle electrical system?
Any help you can provide would be greatly appreciated. Thank you.


supereal    -- 01-20-2010 @ 10:55 AM
  Most of the modern 12 volt coils have a built in resistor. Without knowing the current draw of the coil, it isn't possible to know how much resistance is required. Some 12 volt coils, such as some Mopars, are actually to run on 6 volts, and were "goosed" with a bypass circuit to aid starting. I'd use a coil with a known built in resistor on 12 volts. As to polarity, if you are using a negative ground system, the (-) side of the coil goes toward the distributor. On a positive ground system, it is the other way around.


carcrazy    -- 01-20-2010 @ 11:46 AM
  Thanks Super. The coil was purchased from MAC's. It came in a box labelled: Ignition Coil/12 Volt/1.5 ohm/Black and made in China. When shaken fluid can be heard sloshing inside of it.


supereal    -- 01-20-2010 @ 3:14 PM
  I'm not familiar with that coil. Most NAPA stores carry the round 12 volt coils that don't require an external resistor.


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