figueras

HI,
I have a chevy express 2500 from 1997.
The temperature always shows at the minimum level less than 100.
This implies that the combustion is not good enough, and the fan never works.
I already changed the sensor, but nothing changed.
-Do you have some idea..where is the next pace where I should check?
-where can I find a wiring diagram for free...i was googaling and it was impossible to find.

thanks in advance