Rennen

I'm curious to know if I have some other problem with my car that I need to pursue or if I'm really just dealing with coils that are not suitable for my car or are just plain cheap. When I pulled my coils the other day, it was clear that the second coil was heading in the same direction as the first coil that fried. Wax had accumulated outside the coil inside the hat.

When I called Vertex, the guy asked me if I had heat issues with my car. I responded no because the oil temperature sensor sits rock solid between 8:00 and 9:00 on the dial. I can't think of anything else that would cause this.

I found 2 new Bosch coils today at another vendor so I'm going to put those in when I have the car broken down for the wires. I'm really hoping that the coils and wires will resolve my problem. Fingers crossed...will know by the weekend.

warmfuzzies

IMHO dead shorts or very, very, heavy loads are the only things that would cause this.


kevin.

Geoffrey

Very high duty cycles can overheat a coil as well.

jimq

If it got hot enough up there to boil a coil then your engine would be totally cooked! Your blower motor isnt spewing hot air at is it?

Rennen

Ok, so let's talk about those things. I actually consider them both the same thing unless you're talking about an internal short in the coil. There really isn't anything going on under normal operating circumstances that would yield extra load except for a short, right? Persumably a ground fault in a plug wire is not going to cause this because, as someone rightly pointed out in another thread of mine, the coil doesn't care where it discharges, so a point discharge into a plug wire isn't going to affect the coil. An external short would have to be a constant short of ome kind, don't you think? Apart from that, then the coil would probably have to not be built to handle the normal load of the car I think.

Heirsh

Coils being fed too high of voltage? I seem to recall having to install inline resistors to coils way back when (to drop the voltage). I dont know how much voltage these coils use, but if its too high that could do it.

warmfuzzies

Thats in the most part correct, an internal short is the most likely fault, and they are in the main due to poor build, or poor parts. remember they are a coil of insulated wire......wound may hundreds/thousands of times..in the poor quality stuff I've come across its due to the winding machine miss-handling the wire and breaking insulation, and external loads causing the insulation to break down and then internally short.

Don't forget though a spark plug provides a degree of resistance to the coil......but in my limited experience I've not known a coil go bad like this, though I would have to say its possible.

kevin

Rennen

I don't think that's happening. The car runs at a normal temperature and all seemed fin until the blown coil on Saturday.

darth

I think Geoffrey's comment about duty cycle might explain it. Coils are meant to charge/discharge which is determined by the distributor creating a path to ground (i.e. sparkplug) for them to discharge to and engine speed. If you turn the key past the accessory position and 12 volts is always applied to the coil (i.e. 100% duty cycle) for an extended period of time the primary coil winding would probably heat up and melt the wax which could in turn cause the primary winding to short out to the secondary winding, then you got problems. Maybe you've never turned the ignition past the accesory position - but there could be a short in the ignition switch which causes 12 volts to be applied to the coil. Just make sure you don't have 12 volts going to the coil any other time other than when the ignition is turned to the run position. On the other hand maybe you did get 2 bad coils of poor quality.

Hope this helps
Bill
90C2

Geoffrey

Well, that isn't exactly how a coil works....There is always 12v applied to the coil (just windings of wire) so it means that there is 12v going back to the output channel on the ignitor. Since the ignitor is an open circuit (key on, engine not running), no current can flow, therefore, no strain on the coil. The coil only has current when the ignitor (controlled by a square wave from the ECU) connects the output to ground.

jimq

If he has the old ones in and they dont melt guess that points to crappy coils?

Rennen

Now here is an interesting thought, and I'll tell you why. My battery seems to have an inclination to drain when the car sits and I wonder if perhaps there is a clue there. When I replace the coils, I assume I could throw a VOM across the leads and see if I have any voltage there any other time.

Rennen

Excellent point.

darth

I guess I tried to over simplify things. The point I was trying to make is that current flowing through the primary winding could be causing the coils to heat up and melt the wax. I can't imagine heat from the engine could do that and I'm skeptical that even the current produced by 12 volts applied to the primary could do it but if the coils are of poor quality, maybe. Rember RedRS that when measuring voltage at the coil that if there is 12 volts applied to it and the there's a path for the current to flow to ground you won't see 12 volts on the VOM but rather a voltage determined by the resistance of the primary winding. It would be better to put the VOM on the current setting in series with the 12 volt wire (i.e. put the meter in between the wire and the coil) and see if current is flowing. If you see current flowing when the ignition switch is in the "OFF" position this is probably your current draw which is killing your battery. If you see current flowing when the ignition is in the "ACCESSORY" position this is not good either.

Hope this helps
Bill
90C2