In school I hear repeatedly that in order to be a good electrician you have to know how to troubleshoot; and that consists of:
Knowing the theory on how your system operates and Knowing how to use your test instruments so that you can tell if your system is operating properly.
A couple of weeks ago my foreman and I were working on a fire alarm system. We had to have the system turned off so that we could relocate a box and re-splice the wire.
Before the system was turned off, the system was all green. But after we performed our work and turned the system back on the panel was showing an error message; and since we performed work on the system everyone was pointing the finger at us.
I can remember the words of my foreman “We aint about to be chasing no ghosts”. Because all we did was move a box and re-spliced the wires.
So we got out the multimeter and by knowing that in a fire alarm system the wires loop back to the panel. We tested our splices and then we went to the panel were our wires looped at and tested for continuity and all six loops were ok.
After testing and proving that our wiring was ok; one of the people in charge of the panel called someone and they told him to reseat a card that was in the panel. After he reseated the card the system was green again.
Now if we did not know the theory behind how the fire alarm system operate and did not know how to test for shorts and continuity we may have been there a long time trying to figure out something that did not have anything to do with the wiring.
So don’t chase ghost, know the theory behind the system you’re working on and know how to use your test instruments.