WELCOME to LMF.
You will need to know basic things about the circuit you are checking ... most 'safety' switches are normally closed, and function by opening the circuit...
Some switches are a multi function switch, like a PTO switch, it has both a normally closed and a normally open part... allows the starter to operate only when the PTO is OFF...
Some systems use relays, some have low oil, over temp or operator present switching...
So the biggest help in trouble shooting, is a good understanding of how the circuit is suppose to function..
:smile:KennyV