When equipment is down, it's tempting to skip steps that don't directly contribute to getting the equipment back online. But an equipment failure is much like a crime scene. If you erase vital clues, you won't catch the culprit.
Before you start disturbing the evidence, document everything. You want to produce an assay you can compare to baseline test data. Photographs are highly recommended.
Don't make repair techs have to stop and think about what to document. Save time by providing (in the repair procedure) a precise As Found data sheet specific to that equipment. The more complicated and/or critical the equipment, the more data this sheet should call for.
Ensure the order of the data fields reflects the natural order of data collection. For example, oil level and pressure might normally appear in sequence because of alphabetical order. But what if the temperature and pressure gages are next to each other on the front panel and the oil level gage is in the back? Put all the steps in speed sequence.
Also consider the picking up and setting up of measurement equipment. For critical equipment, use a stopwatch to work out the most efficient sequence. Minutes add up.