I would first check the connections. Make sure you have a good power connection and ground. If that doesn't fix it I'd have a pow wow with Chevy Duty. The motor could be bad or made for a different application. It could be made for a squirl cage fan instead of regular blades.

Save a life, adopt a senior shelter pet.
The three main causes of blindness: Cataracts, Politics, Religion.
Name your dog Naked so you can walk Naked in the park.