Megger an ignition coil (helpfull or harmfull)?

[frankiee]

Would it be or any benefit to megger an ignition coil to test the condition of the windings?
The step up voltage would be very large therefore I would guess that it would only be done from high output to the low voltage input.
Would such a test be beneficial to evaluate the condition of an ignition coil or just a waste of time?

 

[blackwed]

Aren't insulation resistance tests done with a DC voltage?

DB

 

[zeitghost]

I think that an ignition coil is actually an autotransformer, so the LV winding is connected to one end of the HV winding.

Don't know what connecting a 500V megger across the HV winding would prove one way or the other apart from simple continuity of the HV winding.

 

[blackwed]

The megger's supposed to give an indication of the condition of the insulation resistance to ground. Since the coil operates at several thousand volts on the high side, a 500 volt megger may or may not reveal a problem. I don't know what kind of voltage the low side is insulated for. Since the operating voltage there is 12 (or less) application of 500 volts may be a destructive test.

DB

 

[frankiee]

Sorry for the question.
To think of it now after reading the replies it was a dumb question.
I was just looking for a more sure way to test an ignition coil when they get hot. I had figured that they must internally short when the saturation time is too long. Or when the insulation gets old and weak.
But now to think about it, where would the current go.
I should have asked what happens to the ignition coil when it over heats and stops working until it is cool again.

 

[MikeHalloran]

I suspect that more coils die from being tested than from anything else. I.e., when you cycle the primary without a properly sized spark gap connected to the secondary, where does the current go? I think the answer is "through the insulation". Once that happens, once, the coil is scrap.



Mike Halloran
Pembroke Pines, FL, USA