Would a continuity check work on an ignition coil?

[Corytrade]

Just using a basic AC/DC meter from sears, and touching each end of the ignition coils (spark plug side, and plug in side), should a continuity check prove if it's good or not?

 

[Rich Rohrich]

You'll need to test the Primary winding resistance by measuring across the two little electrical connections, and the Secondary winding resistance by measuring form the center (plug wire connection) and the power side electrical connection. You'll need a Yamaha service manual to get the correct resistance readings to compare against.

 

[motometal]

Of course Rich is right. What I have done...and what would probably still work as long as basic coil design hasn't changed...

work in a room dark enough to see spark. Put a plug in the end of the cap. Connect the metal base of the plug to the metal part that bolts/grounds to the frame (probably one end of the laminations). Get a 12 V source, battery charger is handy. Connect neg of 12v source to base of plug and/or coil ground, and intermittently connect the + to the positive of the primary (this is the smaller connection). I think the spark is created by the collapse of the magnetic field, so you need to "tap" the 12V+ wire on the connection several times, you should see a spark.


Measuring resistance is a good test but every once in a while on a coil or stator I find one with flaky windings that check good on the bench, but open up with the slightest heat or vibration.

 

[oscaman]

another and easier thing to do is to borrow a known good coil and temporarilly subistute it. Coils can be tricky !! (affected by heat and vibration etc)

 

[MrLuckey]

Measuring resistance is a good test but every once in a while on a coil or stator I find one with flaky windings that check good on the bench, but open up with the slightest heat or vibration.

Yup, if you want to be sure, the best way (aside from swapping with a known working unit) is using a megger putting a load on it.

 

[BSWIFT]

Yup, if you want to be sure, the best way (aside from swapping with a known working unit) is using a megger putting a load on it.

Megger =
1. A good coil,
or
2. A definite bad coil.
The megger will give you a go/no-go result. If the coil is working some before this test, it will not work at all after this test.
But as stated by Motometal, the resistance values could read within spec and still leave you with a bad coil. All very good means of testing a coil. Be sure to check your ground connections.