Posted by Bruce (VA) on September 25, 2012 at 18:49:09 from (18.104.22.168):
In Reply to: 12 v coil posted by pconnie.ks on September 25, 2012 at 17:54:56:
Coil problems are difficult to diagnose. For starters, round coils are pretty robust & square coils arenít (because of the difference in insulation used), but neither one will hold up to a poorly done 12v conversion that allows too much current to the coil or leaving the key on (see tip # 38). Too much current creates heat which melts the insulation. Insufficient resistance in a 12v conversion will do the same thing. Rarely do coils just ďgo bad.Ē
As others have said, there are a few ways to see if a coil is bad, but itís not possible to determine if a coil is good w/o some expensive testing equipment. If you detect a dead short or high resistance in the coil w/ an ohm meter, itís bad. If itís cracked, itís bad. If a sidemount coil w/ battery voltage to the primary will not jump a ľĒ gap from the secondary wire to the block, itís bad. But, here is the hard part: even if you do not detect a short, even if it will produce a spark, even if itís not cracked, that doesnít mean the coil will work when itís hot & under a load. So, itís a process of elimination. If the tractor starts & runs fine for 30 minutes or an hour then cuts off & refuses to re-start, and you checked for spark at the plugs & it had no spark at all, AND you have the correct voltage at the coil thatís a good sign that you have a bad coil. Let it cool off, restart it & if you have a good spark, odds are itís a bad coil. But, even then, you might end up w/ a spare coil on the shelf!
Bottom line.......coils do go bad, but I'll venture a guess that 75% of new N coils sold today are sold to folks who do not understand how to diagnose a poor spark problem or how a coil works. So, for those who donít know any better, in a no spark situation the first suspect is usually the coilÖÖand, more often than not, it isnít the problem.
So, what problem are you having that leads you to suspect a coil failure?
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