Learn to use multimeter, choose a video:
Learn to use multimeter voltmeter: • Video
Learn to use ammeter (measure current): / ffjl-kkocji
Learn to use ohometer (resistance meter): / jx5ibu6yaku
Voltage, current and resistance relationship, OHM law: / 9bfq8ng5kuu
When we have doubts about whether a relay in our car works correctly or not, the multimeter is one of the ways of knowing if its operation is bay or not.
Using voltage, resistance and continuity measurements with our multimeter we can determine if a car relay works properly as I show you in this video.