6 volt to 12 volt

I agree some meters arent real good at reading those low ohms values, but actually I far prefer my old reliable Simpson 260 Analog meter versus my new fangled digital which I just dont trust.

NOTE 1: If you have a true full 12 volt rated coil (some call internally ballasted) you DO NOT use any external ballast resistor.

CAUTION: A true full 12 volt rated coil may be labeled "12 volts" or "12 volts no external ballast required" HOWEVER beware a coil labeled "12 volts for use with an external ballast resistor" is in reality a 6 volt coil and DOES REQUIRE an external ballast (just like it says DUH), otherwise the coil runs hot and the points burn up prematurely. The best SURE way to determine if its a 6 or 12 volt coil if youre unsure is to measure the coils primary winding resistance between its lil + and - terminals as Bob n Jim referred to.

Bob n Jim,

Far as I know the DC resistance in the typical points n condensor type of coil primary winding between its lil + and - terminals is around 1.5 to under 2 on a 6 volt or 3 to 3.5 or so on a 12 volt. Ive seen different types n brands that all read a lil different.

The DC resistance from any terminal (+ or - or high tension tower) to its case/frame ought to be extremelyyyyy yyyy high essentially an OPEN CIRCUIT otherwise the high voltage might arc over.

The DC resistance from either the lil + or - terminals to the high tension tower (represents the high voltage secondary winding) is somewhere around 5 to 10 K ohms and one would be like 3 ohms difference to the other depending upon which of the lil terminals (+ or -) is internally attached to the high voltage winding (other end of that winding is to the tower)

Bob n Jim QUESTIONS

1) Ive seen conflicting internal wiring diagrams, some show the high voltage secondary (end opposite from tower) internally atatched on the + terminal while others show it attached to the - terminal. Your thoughts?????

2) We all know and I assume agree??? a coil is most efficient and works best if wired in the correct polarity relative to the battery DUH We also know and I assume agree??? a plug works most efficient if electrons flow from the hotter electrode tip to the relatively cooler ground strap, same as how in a vacuum tube the heater heats the cathode so the electrons flow from it to the cooler anode plate. BUTTTTT TT my question is does merely swapping the coils leads change the direction of electron flow across the plugs gap ORRRRR RRRRR would it require the battery polarity actually get changed in order to change the electron flow direction across the plug gap????? ????? ? Im NOT convinced merely swapping coil leads changes the direction of electron flow across the gap but tend to think its the other battery terminal the electrons are seeking a return flow to so ONLY battery polarity changes the flow..... . NOTE dont let conventional versus electron current flow muddy the waters, in BOTH cases Im talking about the most efficient (hotter to colder) electron emission so lets consider ONLY electron flow from the tip to ground strap in either the coil lead reversal or the battery polarity changes.

A curious John T

Gerald J.

Using an ignition 'scope to observe the secondary waveform to the 'plugs will confirm that the spark polarity "flips" when the primary connections are swapped. (By convention, traditionally, ignition 'scopes tend to show the spark waveform upside down, to make it easy to observe, or visually measure, the peak firing voltage, which then goes "up", or more (positive) than the baseline, rather than "down", or more negative.)

My GUESS is that coils originally manufactured for (+) ground use have the secondary internally connected to the (+) primary terminal, while coils primarily intended for (-) ground use have the secondary internally connected to the (-) terminal. I would say the idea is to have the end of the secondary winding most directly connected to the condensor (when the points are open).

However, in actual use, it doesn't seem to make a noticeable difference in spark. After all, the primary resistance of only a few Ohms is the next thing to a dead short, compared to the 6000 to 7000 Ohms of resistance of the secondary winding that is, in effect, in series with the primary winding, when the breaker points are open.

Have you ever thought about the confusion caused when a coil marked "BATT" and "DIST" is swapped, from, say (+) ground to (-) ground? "BATT" becomes "DIST" and "DIST" becomes "BATT". Actually, marking the terminals (+) and (-) sure sounds like the best plan!

I hate to contradict you, but that's NOT the way a standard "round-can" ignition coil works.

There should be INFINITE resistance from BOTH primary terminals, AND the secondary "high-tension" output tower connection to the coil's metal CASE.

The resistance of the primary windings was covered previously.

The resistance FROM either of the primary terminals TO the high-tension output is typically 6000 to 7000 Ohms. (That measurement will differ between the 2 primary terminals by the amount of primary resistance.)

What does your Ohmmeter read, with the leads shorted together? What range are you using?

Whether or not you can use the coil without a resistor depends upon the coil's actual primary resistance.

The resistance of the coil's primary, plus the resistor, if used, MUST be AT LEAST nearly 3 Ohms or more, or the coil will overheat in use, and the points will be carrying too much current, and point life will be short.