Posted by John T on July 18, 2019 at 18:18:06 from (45.16.200.171):
In Reply to: 12 volt coil help posted by jm. on July 18, 2019 at 17:54:02:
You ask "I want to know what the restience should read on a 12 volt coil that does NOT use an external resister"
A full true 12 volt coil that uses no external ballast "typically" would have in the range of 2.5 to 4 ohms, many around 3 ohms average. Reason being its best if the points aren't switching much over 4 amps so 12 Volts/3 Ohms = 4 Amps
A coil labeled "12 Volts" or one labeled "12 Volts not for use with (or no ballast required) ballast resistor" is a typical full true 12 Volt Coil and would be in the 2.5 to near 4 ohms range...…...
A coil labeled " 12 Volts for use with ballast resistor" is more like a 6 volt coil in which on a 12 volt tractor the ballast drops 6 volts leaving 6 for the coil.
Some 12 volt cars n truck n tractors used a 6 volt coil PLUS an external series voltage dropping (12 down to 6) ballast resistor. Some had a ballast by pass when cranking scheme to improve cold weather starting
Does it have a ballast (typically 1.2 to near 2 ohms) or not ???????????? if so and its good and works YOU NEED A 6 VOLT COIL. A ballast PLUS a 12 volt coil would give a weak spark !!!!!!!!!!!!!!!!
Most typical causes of no fire are oil or film (some new points have protective coat that needs cleaned/removed) or oxide coated or burned pitted points ALWAYS CHECK POINTS FIRST and insure clean n dry no oxide coating or film or oil and gapped correct. A bad condenser can also cause ignition problems !!!!!!!!!!!!!! Sure the old one is ok ?? Many new out of the box are bad while the old originals are still fine ……… See my Troubleshooting Procedure below
If you need more detailed ignition troubleshooting click my link below
You may get several responses and opinions as its an electrical question, here's my response TO YOUR SPECIFIC QUESTION maybe others have different answers
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