12 v coil

[pconnie.ks]

Is there a way to bench test a coil
 

[teddy52food]

Yes, with a coil tester. If an ohmeter shows an open in either circuit it is bad.
 

[souNdguy]

about the same as with a tractor.

of course you can get fancy with a switch, condensor and spark gap too..
 

[Hobo,NC]

If an ohmmeter shows an open in either circuit it is bad.
If a ohmmeter shows its good it still can be bad...
Its a rare event to see a ohmmeter confirm a kill....
 

[Bruce (VA)]

Coil problems are difficult to diagnose. For starters, round coils are pretty robust & square coils aren’t (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 # 3. Too much current creates heat which melts the insulation. Insufficient resistance in a 12v conversion will do the same thing. Rarely do coils just “go bad.”



As others have said, there are a few ways to see if a coil is bad, but it’s 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, it’s bad. If it’s cracked, it’s bad. If a sidemount coil w/ battery voltage to the primary will not jump a ¼” gap from the secondary wire to the block, it’s bad. But, here is the hard part: even if you do not detect a short, even if it will produce a spark, even if it’s not cracked, that doesn’t mean the coil will work when it’s hot & under a load. So, it’s 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 that’s a good sign that you have a bad coil. Let it cool off, restart it & if you have a good spark, odds are it’s 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 don’t know any better, in a no spark situation the first suspect is usually the coil……and, more often than not, it isn’t the problem.

So, what problem are you having that leads you to suspect a coil failure?
50 Tips

 

[JMOR]

[Royse]

[JMOR]

[Bruce (VA)]

LMAO!

I'll save this response for later use..........
 

[pconnie]

using the 4000 backhoe..sputtered then died..no spark..no spark at points..installed new coil..no spark at points..spark at dizzy terminal..pulled terminal.. insulator corner was broke off..replaced insulator..back working..guy at oreillys shook the old coil..determined it is bad..new coil has fluid slushing inside..old coil does not..trying to decide if i want to see if oreillys will take new coil back..thats why i thought i might be able to bench test to determine if old coil is good without replacing it on the tractor..im ate up with arthritis..nothin is funny bout this..thanks for all interest phil
 

[JMOR]

[Dell (WA)]

Phil.......You first asked "Is there a way to bench test a coil". I flunked mind reading, just ask my ex-wife of 32-yrs.

Now you explain WHY you are concerned 'cuz the insulative oil inside the round can coil "sloshes". As a general rule, yer roundcan coil should NOT slosh. Taker back and complain. Don't be surprized iff'n they won't exchange. Usually parts stores have a sign on the wall "NO ELECTRICAL EXCHANGE" .......the mindless Dell
 

[rossow (mn)]

Not relevant to technically testing a coil, but... Both of my 8Ns have been converted to 12-volt, so when I go to car swap meets, yard sales, etc., I pick up new/used round coils when they're cheap, just to have a spare or two or three available for "testing" purposes. Got one new in box for $1 this summer, and another "slightly used" for $3 at a swap meet a couple of weekends ago. The same coils fit my N's as fit my old Novas and Chevelles and '55-57's, so it's easy to swap them around to pinpoint a bad coil. Pretty sloppy approach, perhaps, but it works for me at very little expense or effort.
 

[JMOR]