Strange noise coming from my ER6n...

Just after a bit of advise…the other day I was filtering my way through heavy traffic and when I came to a stop, my bike was making a very strange and loud noise. From listening to it from on the bike it seemed to be coming from the fan - it sounded like it was straining. I continued home, and the noise kept on cutting in and out whenever I stopped (as if starting/stopping when the fan cuts in/out?) It also seemed as though the bike got hotter than normal (but I could have imagened this as it was a hotish day and lots of traffic!). I got home and thought nothing more of it.

The following morning I rode into work, and the noise started again after about 5 minutes of riding. So when I get to work, I checked the coolant level (was fine) and oil level (just in case) and that was also ok. When I finished work that evening, I got on the bike and rode it home. The noise only started this time after about 15/20 minutes of riding (no traffic and only stopping at traffic lights).

During the day today, I took the side fairing off and tried to access the fan…but it looks very complicated/looks like an OMC job.

Does anyone have any idea what could be causing this, and any idea how to fix it?