Ignition coil unusual failure

[JOSEPH BRINCAT]

Hello all, Working on a Champion with the Bendix Sintella mag. The coil is bad, but the failure mode I found unusual. The coil primary and secondary both check OK with the VOM, so there is continuity thru the windings, but no spark when testing with the Mertronic. So, I guess than rather than the usual “open” in the secondary there must be a high voltage short to ground in there somewhere. Just a curiosity I thought?

Joe B

[David Stanton]

High voltage is likely jumping across failed insulation inside the coil somewhere in the secondary finding a shorter jumping path to ground than through the spark plug gap, and yes – an Ohms check will not show this.
Dave

[Author]

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