There is no fan switch on these cars the fans as with any modernish car are ECU controlled. I suspect a dodgy NTC (AKA CTS in older speak) sensor as this is what provides the temp info for the fans along with other things when the connector is removed the fans should run all the time as it registers a fault then when reconnected the fault disappears and fans should go off, although I would think the car would not drive well if this was the case.

IIRC the Focus CANBUS keeps the temp gauge at half as there was complaints when new about high temps, but it should read hot when overheating.

As a emergency measure you could use the A/C as this SHOULD also switch on the cooling fans so this would be a easy test.

Martin