Is it necessary to disconnect the battery s to pull out, check, or replace a relay in the circuit box?

 

Rick

          No,  pulling them with the batteries connected and the key in the off position will not hurt anything.

Easy way to test relays is take a known good relay like the horn which is a smaller relay and swap it with what is questionable if the problem goes away then the relay failed. Like two years ago I lost my A/C relay I swapped it with a known good relay and A/C started working. The next town I came across I stopped in just purchased a new relay.