- Thread starter 1948jr
- Start date
oints generally "burn" as a result of arcing which can be aggravated by wrong or bad condenser OR by too much coil current (your question). Typical correct current is around 3 1/2 to 4 amperes, when stalled. Coil current is a function of voltage (6 or 12 (7.2 or 14.4) and primary circuit resistance. Primary circuit resistance consists of coil winding resistance or coil winding resistance plus resistor resistance. In either case you can obtain the magic 4 amperes either with the proper coil primary resistance or proper coil+resistor values. I have coils ranging from 0.5 Ohms up to 4 Ohms primary resistance and the same 4 amperes can be obtained by using a 3 Ohm coil & 12v as can be obtained by using the 0.5 Ohm coil + a 2.5 Ohm resistor. In either case, we have 12/3=4. There are many roads to the same place.
Bob (Aust)
Well-known Member
I have never owned an engine with 12 volt ignition and 6 volt coil and resistor combination. For $15 or so, I'd rather have a 12 volt coil.
gave you the answer......correct current level keeps them from "burning up"!
Maybe more hand holding is in order. You don't see a resistor in diagrams, so why not burning up? Well, just maybe someone used the correct coil, let us say with a 3 to 4 Ohm primary resistance, such that they obtain a safe/correct current level.
o the best of my knowledge, the ONLY car that ever came from the factory with a coil with a built in resistor was 1953-1955 Chrysler Imperial (AutoLite coil). Now, what virtually all posters are calling a "coil with built-in resistor" is in fact not! What they are is a coil wound with appropriate wire length & diameter & metal properties to yield those higher primary resistance measurements, such as 3 instead of 1.5 Ohms. I haven't a clue as to when the 3 & higher Ohm primary coil windings first appeared.
hear you, but.......until someone cuts one open & pulls out that resistor, & shows it to me, I will continue to say that there is no resistor in the coil can. A resistor is a discrete component, it is not the resistance distributed throughout a length of wire. Not semantics, either, just fact. All the wiring in your house has resistance, but is wire, it is not 'a' or 'a bunch' of resistors connecting panel to outlets & lights.
Bob (Aust)
Well-known Member
12 volt coils have been installed on Ferguson tractors since the TEA20 went from 6 volts to 12 volts around 1949 - 1950. Whilst US built cars retained 6 volt ignition into the 1950s, UK and European cars were generally 12 volt ignition from the 1920s.
I don't believe there is such a thing as a "12 volt coil with built in resistor".
There are 6 volt coils, there are 12 volt coils; and there are those owners who are too tight to buy a $15 12 coil when they upgrade, so install a resistor in series with the 6 volt coil to drop the primary voltage back to 6 volts. Then wonder why they have starting and running problems........ :lol:
Joe Scribner
Member
several old 12V coils that have said "internal
resistor" I have never found a separate resistor.
My shop teacher back in trade school explained it
to me this way. The different internal resistance
is strictly a function of the size and number of
the windings in the coil. The finer the windings
the higher the resistance and if you add more
windings you get higher resistance. It's pretty
basic science if you understand that any conductor
has a specific resistance to current flow.
Bob (Aust)
Well-known Member
Why worry about primary coil resistance?
Primary input voltage is a function of the number of turns in the primary coil. Primary resistance is a function of primary coil wire diameter and length.
ow! Nice clean looker you have there! None of mine have even come close to clean since they left the factory. As to marking input voltage, well.............that is just too simple ......and sometimes when they do, they lie. Example Ford 9N, 2n, 8N (front distr) coils marked 12v are not really.......they still need a resistor. Pitiful isn't it?(quoted from post at 15:28:23 12/06/13) Why not simply mark the coil with the primary input voltage?
Why worry about primary coil resistance?
Primary input voltage is a function of the number of turns in the primary coil. Primary resistance is a function of primary coil wire diameter and length.
Bob (Aust)
Well-known Member
Bob in Oz
'53 TEA20
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