Thanks Jo, sorry I did not get back sooner I was out of town.
"why you want to switch it off ?"
Simple, If I run a sequence that finishes at say 2:00am and I sleep to 8:00am the fan will have been running for 6 hours collecting dirt etc. for no purpose.
What I would like is a software command that once a sequence is completed, and the camera has been 'warmed' to shut the fan down.