Just a note for anyone who has ever run into a case where customer complains of hearing an 'oscillating' sound coming from their refrigerator but couldn't find problem.
I ran into this on a Frigidaire NextGen SxS with the ADC control and standard evaporator fan motor. The motor sounded as if it were very quickly starting and stopping, then would run fine. Very intermittent issue. Checked everything possible. Motor good, voltage to motor good, wires OK, no obstructions or excessive ice, etc. Had a good fan motor with me and changed it out to test, with same results. After checking everything else possible, I replaced the ADC and that solved the problem. Seems that my meter, even though it was a good digital VOM, couldn't detect the voltage drop outs fast enough.
Gotta love those mystery calls!
Have a great day all!