What causes coil to die?

As the title says. My coil decided to go out as I was out and about a couple of days ago. I never had one go out so quick before. I was driving up a hill hill and the JEEP sputtered and died. I flat towed it back home. Fortunately I had my old one. The one I had was from Genessee Products and was installed the same time I installed my Petronix.

I only had about 400 miles on it, so it seems a bit premature for it to go out. Should I look for something burning out my coil or is it just a fluke that it burnt out so early and I should not be concerned.

Thanks

 

A coil is a fine winding of wire incased in oil or in some potted in a resin /plastic. Since the wire is very fine sometimes shock and vibration opens the wire. If a condition exists where a lot of heat is on the coil and the current is high the resistance increases and the wire might burn out. Some coils are externally resisted, and some are internally resisted, if you use the wrong coil the life of the coil is shortened. They are pretty durable, but they do fail. Can anyone predict when the light in the refrigerator quits working, electrical things fail sometimes.

 

I had a long conversation with a transformer maker a few years ago. He said that transformers (and coils) just wear out. Every time the coil is energized, the magnetic field creates a force that pushes the wires against the former. Metals like copper and aluminum (not steel) can only withstand a finite number of flexures before they break. Even the tiniest stresses cause cumulative metal fatigue - this is the same reason why airplane fuselages have a finite lifetime. Steel, however, is a most excellent material that will not accumulate fatigue if the stresses never exceed a certain value.

<edit> So, about the premature failure, in electronics it's called "crib death." The likelyhood of failure of electronic devices starts out very high - when manufacturing defects are realized - and then drops after some time, and slowly increases with "old age." Humans follow the same curve, where infants and young children are most at risk. However, once you pass a certain age (85? 90?) the likelyhood of dying does not increase - that's rather remarkable.

 

It's my understanding that the ones in oil aren't as durable and will fail if you do a lot of off roading.

 

You can kill a coil by leaving the key in the on position over night. Don't ask how I know.

 

You can kill an ignition system by running it with a wire disconnected for too long. The field energy in the secondary windings WILL discharge somewhere. If the field can't discharge its energy by sparking across the plug gap it'll pick the next most convenient path to ground. Maybe it'll arc across the distributor terminals, maybe it'll punch through the insulation between the coil windings and the coil canister. Electronic ignitions can be ruined very easily this way.