Octavia Scout Radiator Fans

Looking for advice on a cooling fan issue. I had a similar problem with a golf mk4 and suspect it is the fan control module in the cooling fan. Fans start  when car is cold and engine off. Turn on ignition fans stop. Turn off ignition and wait 10 secs and fans start- and keep running until flat battery. The problem is intermittent some days does not happen. Local autoelectic specialist looked at it on a day the problem vanished and could not find an issue with any elements of the circuit, so I need to wait for it to become more frequent. Meantime I am disconnecting the battery overnight to avoid a flat battery in the morning, which is ok but makes locking up problematic. I have found that if I remove fuse 24 in the engine bay it stops the fan  but I don't understand why this is as the manual says fuse 24 is "activated charcoal filter, and EGR"- this would be an easier way to protect the battery when the car is parked up provided the fuse is really also breaking the fan circuit. Ideas? Jerry