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Cal, More typical resistances of coil primary windings as measured between their lil + and - terminals is: 6 volt coil..... .. 1.25 to 2 ohms 12 volt coil..... . 2.5 to 3 ohms and over NOTE: A coil thats labeled "12 Volts for use with an External Ballast" is in reality a 6 volt coil, so dont let that fool you. Yes, such coils are for use on 12 volt systems, BUT ONLY with the added series Ballast Resistor. A true full 12 volt rated coil is simply labeled "12 volts" or "12 volts NO external ballast". Its possible to do a preliminary low voltage ohm meter check on a coil which will only show if its BAD, HOWEVER, even if it passes it dont necessaruly mean its GOOD cuz more common problems are high voltage insulation brreakdown which the simple ohm meter test will not show. To test all you can do is measure the resistance of the primary and secondary windings and if EITHER fail its bad. The primary resistance between the + and - terminals ought to read 1.5 to 3 ohms or so (see above) with near infinite resistance to case but if its an OPEN circuit, the coil is bad. Likewise, the secondary resistance to the center high voltage tower would be in the several thousand ohms. If its an open circuit its bad or if its shorted to case its bad. Another check to see if its bad although not necessarily good, is to remove the coil wire from the cap (leave coil end intact),,,,, ,place that bare end to within 1/8 inch from tractor steel, turn her on and insure theres voltage on the coils input (from switch, NOT to distributor) terminal,,,,, ,remove the lil coil wire to the distributor and use a jumper wire to short/flash the terminal to ground (i.e. make the coil conduct current) and each time its connected but then removed, a spark ought to jump that gap. HOWEVER thats not an accurate test in the long run (still shows if bad cuz if no spark shes bad) as coils are more prone to fail after they are warm and when the points are opening n closing rapidly. You can party test a condensor with an ohmmeter but again, only to see if its really bad, but you wont know fer sure if its good. It should read like an open circuit (near infinity ohms) to a DC ohmmeter or test lamp and NOT a short or else its bad. If in doubt just try a new condensor. NO, theres no difference in the points or condensor necessarily cuz of use on 6 or 12 volt systems, the difference is in the condensors microfarad rating which is designed to match the coil its being used with. Most any of the typical ignition condensors will still work to a great degree, even if NOT a perfect designed match. if too big, no spark, if too small, she still sparks but the points will burn up quicker. The most common cause of no spark is the points are burned or oxide coated or pitted or carboned up. Check that and for the proper gap. Lemme know and post back any questions. If you need I will post a long winded troubleshooting procedure for no spark. Best wishes n God Bless John T Nordhoff in Indiana, retired Electrical Engineer
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