Elitech WJL-6000S Freon Leak Detector Halogen Gas Sniffer Refrigerant AC Leak Tester R22 R410A R134A R1234YF

When you check car a/c for leaks, do you have car running and a/c on, or do you check with engine off and a/c off

When and why would the replaceable tip need replacing?

Do you actually find the led indicator really useful? have you actually seen a case where the leak level is between red and green?

Is it sensitive to drops?