I'm not very sure but everytime they've checked my car they say it's everything ok

Hi
I have a xc90 awd 2.4 diesel and I have a problem with the cooling sistem..everytime the car starts to overheat the cooling fan didn't work until I turn of my car..
When I'm climbing mountains or hard roads in summer the car starts to overheat and i'm obligated to turn off my car..Or in the ...