Mondeo remains cold

who can help? mondeo BJ 1996 the temperature indicator always stays in the “cold range”, but moves something. Even after a long drive the heater only brings a lukewarm air. There is the thing with the 2 cool circuits that permanently runs the fan. I checked, even after driving the highway the fan does not run. why does this stay cold??? before someone asks, cool water is in there up to max. Thanks for all the answers