Make sure your rear wiper switch is not on....(ssuming the wiper is not moving).....Happened to me. My rear wiper motor was locked up. Aparently I tried a few times using the switch to get it to work, and accidentally left the switch on with the motor stuck. Every 5 or so days the battery would be dead! Took me forever to diagnose it, but the giveaway was the relay would tick! Something to look into just in case.