use a Digital multimeter and measure votage on the positive side of the clip that connects to the fan.
Here is my procedure for checking my fans. If you have a/c just turn on your a/c. this will turn on both fans. If both fans come on everything is good and you'll need to check the fan switch cause this is what turns the cooling fan on when the engine gets hot. If the condenser fan comes on and not the cooling fan. Take out your multimeter and measure voltage on positive side at the fan. If theres voltage, you have a bad fan motor and if you don't have voltage, you'll need to check at the relay. eventually you'll eliminate sections of the wiring to find the problem. By the way you'll need a wiring diagram. Let me know if you need one.