You can disable the fan check by editing and remaking bmminer, which somename must have done. With the default code, even if you disconnect both fans you will still see the "Checking fans!" message in the logs.
"which somename must have done" No, I didn't know you can disable it. Thanks for tip. In my setup I use this
https://www.techidiots.net/notes/fake-fan-sensor to fake fan speeds.