The spark of knowledge

There is more to electrical fault finding than protons, electrons and plumbing similes

Published:  29 April, 2015

By James Dillon

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Consider the training materials which accompany typical apprentice level electrical training. They cover electricity at the atomic level; it's all protons and electrons. I fail to see why this is covered at an entry level. Then, because explaining electricity appears to be too difficult, we start drawing comparisons with water - pipes, taps and pressure gauges. Perhaps it's just me but plumbing and electrics don't usually mix too well. Next, we considered Ohms and Watts laws; the triangle equations (including a smattering of history about these esteemed fellows). I want to know about practical circuit fault finding and testing for problems, it would make sense to cover the minutiae of the theory once basic and practical circuit testing had been mastered, as the theory would at least fit in to a practically relevant framework.

I recall, I spent many hours being taught this theory stuff without it really having a perceived practical relevance. Personally speaking, when I was at college I was firstly bored by the theory and then over-complexed by water similes, protons and hole theory; I thought that vehicle electrics didn't really make sense and just wasn't for me. When we were eventually let loose with practical fault finding sessions the next problem appeared: They majored on testing circuit and component resistances, which we know to be a less than great way to find faults.

Figure 2

There is an often quoted saying attributed to A. Maslow which goes "I suppose it is tempting, if the only tool you have is a hammer, to treat everything as if it were a nail". This sums up quite nicely some of the limited methods which prevail in automotive fault finding. With limited tools, single-minded technicians may apply it inappropriately or indiscriminately. There are many flaws with the resistance-only test method, and if you're reading this and don't know them, you have just identified a gap in your knowledge. I'd respectfully suggest that you get busy and find out why resistance is futile, which will also make you a better technician. For me, effective diagnostic testing can be summed up as "testing the right thing, in the right way, at the right time with the right tools".

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