Carol Martin

Battery drain on civic it has been suggested ac relay gets stuck on and could be the issue problem is I don’t know which relay it is. Every diagram is different nothing is marked ac

tech8

There is a Honda service bulletin (TSB A12-041) regarding a new software update the vehicle did not start due to a low battery. The condition of the battery also needs to be checked and possibly replaced.

POSSIBLE CAUSE
The vehicle’s battery sensor monitors battery condition and the PCM determines charging mode. Based on the sulfation of the battery and customer driving habits, the PCM may not select the correct charge mode.

Edit: I just double checked, your year Civic is not part of the service bulletin, only certain 2012 Civics and 2012 - 2014 CR-Vs.

tech8

Although this may not be the cause of your battery drain issue; to answer your question, this is the AC compressor clutch relay.