https://youtu.be/yw48gKmsy-0?si=lCyRCIn_OHqX-WkD

Hello, new member here with a question about the video in the subject line. How do you determine whether there is a short in the primary or secondary windings based on a current ramp waveform? Paul suggested I create a thread to discuss it and share some data. Thank you!

Hey Mikerowechips! I took this example of a shorted secondary winding off a 2009 Nissan Altima 2.5L:

 

You're looking for the abrupt start to the ramp, along with the missing turn-on oscillation. Beware that a waveform like this does not condemn an ignition coil by itself. Secondary includes the coil boot/wire and spark plug. A short to ground anywhere along the secondary will produce that waveform.

Also know that some coils just don't generate a visible coil turn-on oscillation, or the oscillation may be very difficult to view depending on your scope. A missing turn-on oscillation is not necessarily a red flag.

I didn't have any primary winding short waveforms on hand, so I borrowed one from an older SD video:

 



You're looking for the super tall ramp. The shorted primary will draw significantly more current than a known good. Again, beware, just because one coil draws more current than another doesn't mean a primary is shorted. I've seen more than once when a vehicle owner intermixed coil brands on an engine. As a result, the peak coil current draw varied by several amps.

Ok, thank you for explaining that. I think I understand what I'm looking at now. I will set up some experiments to fully understand the theory.