T350c inner air ventilator not working

[keke99]

Hi mates! I try in english, please try to answer with a very simple english language.
I have an issue with my ventilation in the cokpit in my t350 2004.
The inner fan is not working. When i push the button to activate the inner airflow the lights are working but the fan does not blow at all.
Lights are ok and when I push the upper button when air cond compressor is working normally. BUT as I said the FAN is not working at all.
What and where should I check?
Thanks in advance!