Its a pain in the bollocks when you're trying to warm the bike up in winter before you set off!!!Been meaning to fit a cut off switch since about 2005 but not got round to it yet And I know I'll forget to flip it back when I'm ready to go
It is a safety device to stop the fan motor from overheating when stationary.
Second thing he said was that the fan kicks in to protect the fans plastics (not the motor) from the heat from the headers, it's not to aid the cooling system as I thought.So there you have it (and the reason not to fit a cut-off switch).