My putzmeister hopper fan stopped working and our macanic failed to find problem, help me

either a fuse or a fan motor burnt up , go manually turn the fan see what you hear , or if it doesn't spin freely its probably the fan , there is also a switch on your control panel to manually turn fan on all the time  , I have had temp sensor go out and the fan would not turn on automatically , and you'd have to run it in the manual on position.