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Melted or Damaged Ignition Coil

Bulletin 4002

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All vehicle application with an ignition system


Ignition coil failure is nothing new to the repair industry. What

we are seeing more frequently though are ignition coils that appear to be

melted or physically damaged by heat.


The technical services group receives a fair number of complaints concerning damaged ignition coils due to heat shortly after the replacement of the original ignition coil or possibly repeated failure in its history. It may be easy to assume that the replacement coil failure was due to poor quality or design of the replacement coil, but the answer always goes down a different path. An ignition coil is two separate windings of copper wire, one is the primary winding, one is the secondary winding. A select few ignition coils may have a control unit within but in all cases the ignition coil is only doing what it is commanded to do by the engine control module or a remotely mounted ignition control module.


The driver circuit, or the circuit that turns the ignition coil primary circuit on, is handled by a chip, or transistorized control unit. That chip can be compared to a switch that will ground the primary winding of the coil which, like any electrical device, is subject to failure. The ignition coil, while doing its job, will create heat in the driver circuit. If the ignition coil is required to provide more voltage to the spark plug to complete the ignition event in the combustion chamber, increased on-time of the primary circuit will damage the ignition coil as well as the chip in the control unit. It is possible for the chip to fail intermittently so when the new ignition coil is installed it will appear to function normally, but when the chip heats up it will fail causing a repeat no spark condition. Diagnosing the entire ignition system when a no spark condition occurs will prevent the false sense of a new product failure.


In most all instances this resulting damage could be prevented by performing scheduled maintenance on the ignition system like replacing the spark plugs and ignition wires or coil boots when required. When you have a misfire condition which leads you to the ignition coil, analyze the entire system, not just the ignition coil to prevent a repeat or continued fault condition.

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