Repair begins with understanding how the thing was supposed to work.

Fixing anything is mostly diagnosis, and diagnosis needs a picture of the working version. Without knowing what the thing is meant to do, and in what order, you are looking at parts and guessing, which usually ends in replacing something that was fine. Understanding the intended behavior turns a mystery into a short list of possible failures.

Before taking anything apart, find out how it is supposed to function: read the diagram, watch somebody else’s repair, or trace the sequence yourself. Ask the same question about a plan or an arrangement that keeps failing. Know the design before you start swapping pieces.