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Found this little dwg. on the net for checking coils polarity other than the conventional lead pencil test and the vendors' tester. No specificity for 12 volt neg. vs 6 volt pos. systems.
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I've been thinking about why the coil polarity is important!
A spark is a spark at the plug!
I think I know but the experts hopefully will chime in.
My shade tree experience says it's the gap in the distributor first then at the plug? -
Chicagoland mg club has the best explanation I've ever seen.
http://www.chicagolandmgclub.com/tec...neral/574.htmlComment
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Thanks Tom, wondered if or where the dwg. came from. A few paragraphs down, it says there's no difference in connecting the test leads to read the analogue meter for + or - ground systems ( even assuming the coils are marked + or - but also assuming as taught by theory that electrons flow across the battery from + to -).Last edited by plyfor; 11-24-2017, 09:25 PM.Comment
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With neg. ground (12 volt) , one would think the + meter lead in sketch would be connected to the plug, not the head. The current path through the 12 volt - grnd.. coil would assume to be from + to - across the coil primary..Comment
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Ideally the lead to the plug is negative, no matter which battery post is ground, so the negative meter lead should always go to the plug.
I like to use a high ohm resistor between the meter leads, so I can short out most of the high voltage, rather than sending it through the meter.Comment
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Our 12 volt ( negative ground) coil terminals are marked; so in summary, the ignition switch red wire is the ground leg and goes to the neg.coil terminal. The black wire runs from the + coil terminal to the + j box terminal.
Would assume since the coil is marked that no polarity check would be required.Comment
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some info says the plus is where to check the high voltage, and another says use the minus. I also have seen wiring diagrams showing comman internal connection on both plus and minus. Are different coils wired differently to the + - terminals? Also, I get the same ohm reading from the hi tension tower to either plus or minus. This is on several coils that spark well.
which terminal is the power...10-15-2018, 09:11 PM -
I have what I think is an original slant pole coil in my box-o-stuff. How can I determine if it is a good working one or not?11-28-2017, 09:09 PM -
Today I changed out my coil to the flame thrower 40111. My electric tachometer is hooked up to the coil. Now my tac is showing fast for some reason. Any idea why.09-09-2017, 07:11 PM -
I have read about the big no no about mounting a ignition coil, terminals down on Model A firewall. I have a NAPA 12V internal resistor mounted upside down for 3 years. Brother rumbles by with 72 dodge Demon , nice 340 , while looking around I noticed ignition coil bolted on its side to intake manifold , factory dodge design. the same coil that I am using exactly, He says its been there for 15 plus...05-12-2018, 06:18 AM -
can the 6V tester be used for twelve volt? What changes would be needed to test 12V coils?...02-16-2018, 10:55 PM
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I am looking for some guidance on testing a 6 volt coil with an analog meter. I presume side post to side post will check the primary windings but what should be the setting on the analog meter and what range of numbers constitute an acceptable reading? Almost the same question with regard to checking the secondary windings. I presume side post to center is proper but which side post and what constitutes...06-11-2017, 02:07 PM -
I am looking to purchase a coil other than OIL filled. I see that Summit Racing sells Per Tronix Ignition Coils which are EPOXY filled and Primary Resistance is 1.5 ohms with maximum voltage rated at 40,000 volts.
MY QUESTIONS:
How does this coil match up to the original coll in that it is filled with EPOXY and voltage rated at 40,000 volts?
What is the original coils maximum...10-05-2018, 03:32 PM -
Attached is a dwg. from the net that may be helpful. It also shows how to locate a condenser away from the dizzy and up at the firewall. If an oil filled coil is used, the diagram has the terminals facing up requiring a longer coil to dizzy wire....02-13-2018, 06:15 PM -
We picked up a (12 volt) Standard -no resistor required- UC15T oil filled coil. The oil does slosh around inside. Research suggests these cylinder types can cool better than epoxy filled when the terminals are facing up. The Model A's have the terminals facing down. Does anyone have concerns about this?11-07-2017, 12:09 AM
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COIL TESTER
Coil Tester
By Tom Wesenberg
Here is a coil and condenser tester I made for about $9. The 6 volt relay is 35 ohms and the capacitor connected to the relay windings is 330 microfarads. This combination makes the relay vibrate at a rate to give the coil the same frequency as a Model A running at 1,000 RPM. The higher the capacitance, the slower the relay...08-06-2018, 07:21 AM
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