A maintenance record gives the next worker a history the machine cannot explain.

An object cannot tell you what has already been done to it. It shows its current state and nothing about the repair that failed twice, the part that was substituted, the noise somebody chased for a month. A written record carries that history forward to whoever comes next, and without it every new person starts from scratch and repeats the same discoveries. Most wasted effort in shared work is exactly this kind of repetition.

Write the note even when you are certain you will remember. Date, what you did, what you ruled out: three lines that save the next person, who may well be you, an entire afternoon.