It probably is the fan. My mom had a similar problem. The fan was in the lower part of the freezer and circulated cold air throughout the machine. I took the shroud apart and removed the motor. It's one of those open type, fractional horsepower - called a shaded pole motor. The bearings were dry. oillite bearings in a felt like holder. Also one of the screws were loose making the fan blade strike every once in a while the inside of the ducting. I re-assembled everything after lubing with a very light machine oil - WD-40 will not work here and there was no noise.