automobile ignition coil shorts between turns

Discussion in 'General Electronics Chat' started by Jaguarjoe, Jul 25, 2010.

  1. Jaguarjoe

    Thread Starter Active Member

    Apr 7, 2010
    A friend of mine has a big problem with his ignition system. Every thousand miles or so the ignition coil dies. I know an ohmeter check is not definitive but that's the only thing available to him. On both a brand new coil and a faulty coil, he gets the exact same resistance readings- less than 1 ohm on the primary and 3k7 ohms on the secondary. This leads me to believe it is shorted between turns. I thought that problem only occurred with unloaded windings but I don't see how that's happening here.
    Anybody have any ideas?
  2. creakndale

    Active Member

    Mar 13, 2009
    The fuel injectors (solenoids) on my 1991 Pontiac Grand Prix began having problems just before the 5 year mark. The problem was the solenoid coils were shorting out between turns. They are supposed to measure 12.8 ohms to 13.2 ohms. Only 1 of 6 was within spec. The worst one measured 7.3 ohms. The enamel coating on the coil wire was breaking down due to a defect with the enamel coating. They were all replaced with a fuel injector of a different part number which has been working well for the past 14 years.

    I could never get an answer as to whether this problem was caused by vibration, arcing, heat, etc. Was the enamel coating cracking or melting?

    My suggestions would be:
    1) Buy a coil from a different manufacturer. If he's buying the same model coil from the same manufacturer and they're using the same defective enamel wire, the problem remains.

    2) If this is an older model car and he's upgraded from points ignition to a high energy discharge electronic ignition that might be stressing the coil.

    3) If the coil has been moved from it's original location and it's now closer to the exhaust manifold then it might be getting too warm.

    4) Try to vibration isolate the coil.

    Last edited: Jul 25, 2010
  3. Jaguarjoe

    Thread Starter Active Member

    Apr 7, 2010
    I like #1. Maybe hes just buying the same junk over and over.