You have two simple options to test the fan. Either check for voltage at the fan plug with voltmeter or test light, or run wires directly to the battery. If you have voltage at the plug and the connector and wires look good, the motor is bad. If the fan won't run when direct wired, the fan motor is bad. Let us know the results of one of these tests and we can go from there. Many other things can be wrong, but they are easy to systematically trace.