I have a 15 year old Trane central AC unit. After I turn on the AC, I hear a loud noise and when I go check, the compressor is on but the fan is not moving. I had a guy come change the motor and capacitor, but shortly after the fan stopped moving. I tried turning it off and waiting. Later on, I tried turning it on again and the fan and everything was moving, but after about 1 hour it stopped moving again. I don't know what's wrong.

Is it not under warranty? Usually when the fan runs for a while and cuts out it is the thermal overload protector opening because the motor got to hot. If there is a bad connection somewhere this would explain why a new motor is doing this, when voltage drops, amperage increases and the motor overheats.