Whether you’re talking about the family car, a washing machine, or a widget, if you want to fix it, you first have to pinpoint what is wrong.
That means you have to be able to recognize and eliminate what it is doing right.
At one point in my career, I wrote and taught a basic, generic troubleshooting class. It was designed for copier repair technicians, but I wrote it without any references to copy machines.
I taught that you have to understand what the machine is supposed to accomplish, and to be able to break the process into a sequence of individual steps. Then, you have to be able to identify the step where the process went awry. Once you’re there, finding the source of the anomaly is usually easy – seldom more complicated than choosing between two components.
If you can do that, you can fix anything.