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Is it common for a vehicle to run normally with reversed coil polarity? Just tinkering today and noticed my points wire is going to the positive side of the coil, and my pink ignition wire is hooked to the negative. How could the coil charge properly with the hot wire hooked to the wrong side?
Inside the ignition coil, the primary and secondary windings have many turns wire wrapped around an iron core. They only have a single common connection. Notice that an ignition coil isn't grounded. So why is there a + and - terminal, you might ask?
The coil will operate connected either way, though a coil connected incorrectly with "reverse" polarity will have less energy output at the plugs and also - a permanent reduction in output even when re-connected correctly due to residual magnetism in the iron core, or somesuch.
Note too, the correct coil polarity has nothing to do with the vehicle ground polarity itself, i.e. whether or not it is a positive or negative ground system.
The reason it matters, is what engineers discovered about the way an ignition spark is generated at the plug itself. What we think of as "ground" isn't quite the whole story here, the energy (volts) required for a spark to initiate is very different depending on whether it is generated from the electrode tip, which is at a high temperature, or generated from the relatively cool ground electrode. A spark "likes" to jump from hot to cold, though requires more coil energy to jump from cold to hot. That's why the "40% reduction in output" referenced above. According to the link below it's 15 to 30%. Connected improperly, spark intensity is reduced, the engine will still run though the spark energy output is not optimal for making a good HOT ignition system, under tough conditions, under heavy load, climbing hills, worn plugs.
So if you're like me, this is something important to check during a sleepless night, tossing and turning. My God, is it possible - I've been driving around with reversed polarity at the ignition coil, resulting in attenuated output, the heartbreak of psoriasis, for lo these many years? Get your slippers on and head out to the garage. You'll sleep better. Only takes a second.
"You can also check spark polarity using an analog (moving needle) volt meter. Hook up a voltmeter with the negative lead to the plug terminal and the positive lead to the block. Set the meter on the highest volt range. Crank the engine over (no need to start it), and you should see an upward swing of the voltmeter needle (don't be concerned with taking a reading). If the needle swings down off the scale, your coil is hooked up wrong. To correct it reverse coil primary leads. Do not worry about the coil markings, but make note of them for future reference."
This is a lot easier than the "Pencil" method, and a whole lot less likely to shock the $&it out of yerself. Takes just a second.
Interesting read Tedster! Kinda bummed out now though, because there will be more sleepless nights for me knowing I'm suffering from "permanently attenuated coil output" due to this thing being hooked up wrong. Time to start looking for a new coil I guess!
I did the "pencil test". But only once! It took about 15 min before the feeling came back to my hand. Sure felt like that big yellow Accel super coil had plenty of spark.
All the high power industrial ignition systems I deal with fire with reversed polarity, a negative going spike, because it reduces the wear on the spark plug. These ignition systems are designed to fire in this manner and I've always wondered why the automotive world still uses positive firing ignition systems. Here is a plot of a negative firing system with multistrike capability.
I did the "pencil test". But only once! It took about 15 min before the feeling came back to my hand. Sure felt like that big yellow Accel super coil had plenty of spark.
LOL!! yeah ... I took one look at that diagram and said "No Way Jose" cuz, I've seen this movie before.
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