Actually, it's probably even more basic than that.
I've a rather nice guitar (Hamer) that's got a couple of standard p'ups (BKP MQ P90 & SD something) plus a piezo. Have a gratuitous pic of guitar-on-workbench awaiting surgery ...
Great range of sounds. But it had developed a bit of an intermittent fault that I put down to a wiring issue. Something come loose somewhere and either cutting out or grounding.
I'd opened up the back before, and just decided to leave well alone.
But, got to do it this time.
So, I got out the pencil and paper and started drawing everything out, working out what was what. where it went and why it went there.
I kept plugging it in, and wiggling wires about whenever I saw anything that looked a bit loose or tired. It took me an hour or so to get it all drawn out neatly.
Having wiggled most bits, and not found the cause, I was starting to think that perhaps I'd need to re-wire from scratch. Not 100% a bad thing, as I was going to swap out the MQ P90 for another HB anyway.
Time to plug the soldering iron in.
I was so sure that the wiring was the problem, that I'd not even thought to check the battery, much less notice that it was a rechargeable.
New battery, no more wiring problem.
Wasted an hour, saved a good few more.
Go on then, laugh ...