Drive a fan through arduino IO and matlab simulink

Hello everybody, I have a project in witch i have to drive a 4-pin intel fan through matlab and simulink according to the temperature.The problems when i try to set the fan speed are: a)when i try to set it in real time through the matlab's terminal i can see difference only after around the value 210 and the maximum is 250.Is that normal?I know its impossible to see the difference in low values but still it shouldn't make a difference only above 210. b)whenever i sent values through a simulink's controller and serial send-receive the fan doesn't change the speed at all.

Please lend me your lights, a hopeless student

[Rolfe Dlugy-Hegwer]

Hi klob, thanks for your question. To help others reproduce your issue, please describe your software and hardware setup: Which version of MATLAB? Are you using Simulink Support Package for Arduino Uno Hardware, Simulink Support Package for Arduino Mega Hardware, or something else?