I have watched engineers and the more qualified but poorly paid technicians take a functioning machine/device and “break” it. Then spend hours to days and hundreds to thousands of $$ to bring it back to working order. They simply do not understand that if something is working leave it alone.

On a related note; be careful of those “free” inspections of your home heating and cooling systems. I will almost guarantee you that even if it is now working flawlessly it will have something found to be wrong with it during the inspection.