I have a 1998 528i that is running hot ONLY sitting still. Say picking up lunch at a fast food drive thru. If I have the AC I have to turn the car off if it takes any time at all, but one back on the road temp return to normal. My questions are should my cooling fan run only when the AC is on? If I had air in the system wouldn’t it run hot all the time? Is there a test for a faulty fan switch? Thanks in advance