Engine cooling fan not working
 

Hello!
I hope someone can help. I have a european Mazda 3 2005 1.6i 16V engine code: B6ze
Not so long ago i bought this car. At the summer i noticed the engine cooling fan does not turn on. Neither when i turn on the A/C. The engine heat sensor works fine, and all the wirings are good. the cooling fan is a bosch 1137328148. I already replaced it but it still not working. Checked all te fuses and relays. The blue wire from the ecu have 10.5V output. i think it should have 12.5V (around) The connector have 3 wire a +12V red and pink, a black groung and the blue cable from the control unit. Also there is a 4. cabe at the bottom of the fan. Unfortiunatly i don't know what it does. Only i know it connetcts to the ground.
I would really appreciate if someone could tell me what is the standalone connetcors purpose. Also an electrical diagram would be really helpful. Could be the ECU?
Sorry for my bad english.
Thanks!
Greetings:
Dave