Guys,
Yesterday, after driving over 400 miles with the AC on and shutting my '07 Cooper S once in my garage, I noticed that the radiator fan did not kick in, the way it usually does. I decided to disconnect the battery, and once reconnected, the fan kicked in.
What could it be?
Your input will be greatly appreciated!

Regards

 

Here's a breakdown of the engine cooling system, copied from an old TIS document. Check out the system functions, near the end of the document.

I gave up long ago, trying to figure out when the fan should be on or off. Adding an external coolant temp gauge might help.

 

Wow, that is great info Old Broken Wind.....Thank you for the PDF link.

 

Thank you oldbrokenwind!