Recently our central air unit stop producing cool air and noticed our fan was not turning outside, and was making a loud humming noise, can this fan be replaced without replacing the entire unit :confused:

Yes. Get the model and serial number off the motor and order it.

XenoSapien

Yes, It can be repaired. Is the contactorpulling in? (Guess it is if you're hearing buzzing) Is the compressor running. If so, probably just the fan motor or capacitor. If you take a stick when it's humming and turn the fan. Does it continue to run? If so replace the capacitor. If not the motor. If the motor, always changer capicator with like value (Stated on new motor) at this time. Good Luck. Post back with results

Yes it likely is the capacitor. You can check them with an ohmmeter. Short the terminals and remove one. Apply the leads to the terminals. It is is good, it will start with a high resistance and climb off scale.