WHY WOULD A RELAY GOING BAD CAUSE MY 2012 HONDA CIVIC CAUSE IT TO DRAIN MY BATTERY OF JUICE?

WHY WOULD A RELAY GOING BAD CAUSE MY 2012 HONDA CIVIC CAUSE IT TO DRAIN MY BATTERY OF JUICE? - 1

The relay is shorting internally.

If the relay contact(s) is/are stuck closed, it can provide 12vdc to the whatever is connected to the contacts. The load is never powered down if the relay doesn't disengage.

A relay would be melted if it had that much power going through it. Have the alternator tested. If a diode is bad the battery will drain through the alternator. I did find a rear window defogger relay defective on a Toyota once and the battery would drain through the rear window defogger which does use a lot of power.