Failure at Kenworth T800 Model 2012

Greetings everyone,

I need a favor.
I have a Kenworth T800 dump truck and the manual fan clutch isn't working. It's only working automatically, but I need to get it working manually.
I've already checked the fan activation solenoid and the switch; I even replaced it, but it didn't work.
Please, I need your help because I don't know what else to do about this problem.
Or, please, could you share the electrical diagram for this system or the electrical system manual for this vehicle?
If anyone has it, it would be a great help in resolving this issue.