u/a_millz_214

I recenly bought a 2005 VTX 1300 at auction and got a great deal as the bike only has 2500 miles. I took it for a test ride and it ran great but my overheat light came on once I got back into the neighborhood at lower speeds. I found that my radiator fan isn't kicking on. I am pretty sure I am going to need to replace the fan/motor. How can I be sure it is the fan motor and not something else before buying the part? Also can I buy a cheaper fan motor or do I need an OEM fan motor? Any advice or input is appreciated