A few weeks ago while going on a ride with friends I noticed the fan was staying on soon as I turned on the ignition key. It stays on till I turn off the key. It worked normally before this ride so not sure what is making it stay on now. Bike can be ice cold from sitting all night and fan comes on and stays on now.
The fans are controlled by a temp-switch at the bottom of the left radiator. This is a switched ground, and it's not too uncommon for the swith to rust and decompose inside of the radiator then short causing what you're seeing.
To test the switch, you can just disconnect the wire at the bottom of the radiator and see if the fans come on with your key (grounding the wire will make the fans run).
If the fans do NOT run with the wire disconnected, then replace the fan switch and you'll be good to go.
If the fan's do run with the wire disconnected, you have a short in that wire -- If BOTH fans are running -- you should be able to find the short quickly as the wire is less than a meter long running from the fan plugs to the radiator fan switch only (no involvement in the rest of the bike's harness)