Bumping this thread in hopes of a solution. I have a 2012 Focus that did the same thing. The car was off for about an hour after driving in February and the cooling fan was not running when I parked. When I opened the passenger door with the keys not even in the car, the fan kicked in high. Closed the door and the fan went off. I opened the driver's door and fan also cam on. Hasn't happened since. I just replaced the thermostat due to a P0128 DTC, but wondering if the ECT sensor needs a look. Seems odd to have two coolant related symptoms in close proximity. Lastly, my AC was very weak last summer and I'm wondering if this is all related. If the fan doesn't operate properly it would cause AC problems, right? I turned the AC on yesterday and I did not hear the fan kick on. But I know the fan motor and relay had to work at least twice because it came on when I opened the doors, right? If anyone has conclusively resolved the door open fan on routine I'd very much like to read the solution.
Thank you, Steve