Engine cooling fans

[mannyo]

I believe that the fans for the radiator are multi speed and will vary the speed based on coolant temperature and demand.

I have a feeling that mine maybe running on maximum speed all the time, although I have yet to confirm this.

Yesterday when I started the car after playing with the sunroof we noticed that the radiator fans kicked in very loudly and could easily be heard over the engine. The car had been parked for around an hour without the engine running, and the interior was quiet warm so needed to be cooled by the A/C.

I stopped at Winchester services on the M3 on the way back from Dorset and after returning to the car had a quick play with the climate control. If you engage econ mode from the setup menu (thus disabling the A/C) the fan noise stops and returns when you switch that off.

I gather there are a number of potential causes for the full speed, and I'll slowly check them. perhaps someone can confirm these.

1) One of the two fans has failed, thus the working one is operating harder to compensate
2) The fan speed controller
3) I read something about coils or something like that failing.

Any other reasons?