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Originally Posted by chandu My point was that the press release at minimum sounded like they were putting the blame somewhere easy and not going deeper. |
Thanks for your elaborate reply, much appreciated. Just a few more thoughts and some practical examples.
Yes, manufacturers do take all kinds of precaution against fire happening due to electrical faults. Still, on all ICE cars electrical faults are the number two cause of car fires, right after fuel faults (usually leaks).
And that is before we have DIY electrician messing about with a car electrical wiring.
Using inappropriate wire, in terms of diameter (gauge), material and insulation can cause serious problem including fires. The resistance of a wire is a function of its length, but also its diameter. Half the diameter means 4 four times the resistance.
There is a reason we use different gauge wire for different currents. Just an illustration of current versus proper gauge size (and length). At a given length of wire you can hardly go one gauge down. Let alone if you half the diameter. Then of course, it can get worse, if you use inappropriate wire material as well.
I have a little less faith than you of the so called high quality of workmanship in the automative industry. Be it the car manufacturers or some of their suppliers.
Yes fuses are made to pop slightly above their rated current. But lets have a look at the chart I picked up from the link you provided>
So for most if not just about all automotive electrical circuit it is not a problem that the fuse pops at a higher rating than advertised. As you can clearly see in the graph, at anything under 1 second, the current can be quite a bit higher. But that is for a very short period of time. If you need current protection for under a second you could go for quicker fuses, but in general it is not a problem. What the graph also shows is that for anything over 1 second, in absolute terms, the fuse is supposed to pop very close to its rated value.
And I have seen to many studies and measurement where that, for a variety of reasons, simply does not happen. E.g. a 10Amp fuse would not pop at a continuous 15-20 amp current.
Here is an interesting example of a poorly executed wiring fix I found some years ago in one of my cars. I pulled out the cable and keep it as a Lucky memento. It could have easily caused some serious fire.
the 25Amp fuse never popped!!
As you can see the insulation has (partly) melted and exposed the core in several places.
By and large electrical circuits in cars tend to be designed and installed correctly of course. It is not as if we have cars going up in flames left right and center. But it does happen. More often it happens when people have been messing with the electrical system. On some cars, replacing a simple light bulb can require quite a bit of work. It is easy to damage electrical wires, to get them stuck and squeezed into something.
That is before we consider the option that people make modifications without installing a proper fuse! I have come across those modifications. Radio directly wired into the battery. Foglight directly wired into the battery etc.
It has happened many times and we have a number of members who can testify to that as well.
I think we both agree we just don’t know what happened in this case. It would be better if more detail was provided. Although I am not sure some of our esteemed members would have believed that either.
My point is just this: A fused circuit is not a iron guarantee of the respective circuit not overloading.
Here is an interesting fuse I pulled out of my Mercedes some years ago At the time we discussed it in another thread. The fuse was still working, but as you can see the body of the fuse had actually melted. Go figure!!
Jeroen