Coil Question

Measured across the two screw terminals after isolating from the circuit.
Stan(VA).

Mark

You might want to back up and read my response to your "Spark Plug Voodoo". It explains more about what is going on here. Apparently you are having an ignition problem.

Mark

I bet it would be fun to take an electrical theory course under you. You seem to know your stuff.

Once you see the other side, its facinating.

Mark

I may be steering you wrong here but I have been interested in things like "what parts get changed when you go from a 6 to 12v conversion"? The name of the game is "energy to jump the sparkplug gap".

The points are a switch that lets current from the battery flow through the coil. While doing that it is filling the coil with "energy". The name of the game is to just put enough current into the coil [in the time allowed by what's called "dwell"....hence how long you stay (dwell)] to satisfy the energy requiement of the plug selected.....what is it's temp range and how wide is the gap.

If you run the current too high (put in more energy than the plug needs) you reduce the life of the points as when the points open there is a spark (caused by the coil) and the energy in that spark determines the damage to the points for that firing. (That's why on transistor ignitions, points last forever. A transistor is switched by the points and it electronically does the switching....course they have problems with not enough current to keep the points "clean".

I have been told that 12 volt coils are just 6v coils with an internal ballast (current limiting) resistor. Some have a sign on the side stating that fact. When you Ohm out the primary of your "12v" coil, you should read at least 2 Ohms.

My experience with primary (distributor) circuits is that there is somewhere between 2 to 6 ohms of resistance in the circuit going from the battery thru the coil primary, thru the points and to gnd.

If you go to the auto parts store and get an adjustable ballast resistor, you could set the value yourself. Put the resistor in series with the coil lead mentioned just above. Set the tap on the maximum resistance (6 ohms?). Attempt to start the engine. If you have adequate spark stop there and leave it alone. If not reduce the resistance to 4 ohms then 2 ohms if necessary. If nothing else is wrong you will get the desired result.

Need more, ask.

Mark

Now a purist will come along and say "dummy, that's the purpose of the condenser"..... ..... ....Trruueee. And, for things like automobiles with radio's it suppresses electrical noises that are present when things spark and currents get interrupted in magnetic circuits.

If the current that was charging the coil could be slowly altered and them stopped, when you are through charging and ready to smack the plugs, there would be no sharp rise in voltage across the opening points and hence no damage (primary circuit). The secondary (part going to the plugs)is still doing it's thing and has essentially done it before much changes in the primary. A condenser (capacitor in electronic jargon) is just the opposite of an inductor (coil) in that it sucks up inrushes of current and takes awhile to build up voltage.....neat. If I put a capacitor across the points, when they open, the capacitor would act like a slowly increasing resistance in the coil's discharge and if I select the right value, the voltage across it (while absorbing the current that the decaying field in the coil is generating) will rise slowly enough that it will be below the "flash" value of the points and aha mateees, there will be no spark and essentially no degredation of the points.

I left that out before because you have to eat this stuff a little at a time or it will overwhelm you . A little at a time and it's fun.

Mark

ps Another response to your post from Mr. Hall stated that they run 6v coils until they burn up and they pitch em. Well if you don't have adequate resistance in the primary circuit you can fry the coil too but you will know that well in advance if you monitor the temperature of the coil. If it is hot to the touch and the heat is not coming from the engine your resistor is too small and your coil is on the way out. I'd bet if Mr Hall measured the resistance in his primary circuit there wouldn't be any (so to speak...the wire resistance is there but it is slight)or it would be less than 2 ohms.

Most point failure I have seen is from not having enough resistence in the primary circut to the coil.

Personally I'm glad to see electronic ign. in our cars. I got tired of putting all those points in. Seif.