Have a 2014 JKU and fan started running a lot. Noticed slight over heating issue at idle and with stop and go driving. Needle never went past 3/4. Less when on highways. Went down to normal 1/2 way mark with running heat. After reading other threads I replaced thermostat and drained system cleaned out old fluid and added new recommended coolant. Everything was fine and back to normal for about a week. Noticed today fan running again with slight rise in temp gauge. Turned on heat and gauge back to normal. Any suggestions on next step? Thanks