I have a 2003 MCS that out of the blue started to turn its engine fan on while sitting in the garage with the ignition off. Initally this lasted about 5 min. and then stopped as suddenly as it started. Then the other day I got up in the morning and the battery was dead. When I attached the jumpers the fan started up. The cover of the relay box under the hood indicates two relays for the engine fans (I & II). when I removed the relay I nothing happened but when I removed relay II the fan turned off. I have not reinstalled the relay and the problem has not returned. Could this be as simple as a bad relay (easy fix) or is the problem deeper in the electricals (bad news)? Any insight would be appreciated.

Mike