Just wanted to provide an update on this. I called GE parts and explained the howling sound and from what I had found on the internet, though beyond the warranty, the control board should be covered under a recall as a defective part. When I told the rep I would install the board he said no problem, asked for my address and said the board would be there in a few days, free!
I finally got around to installing the new control board (WR55X10942
) last week and haven’t heard a howl since! The fan actually seems to be a bit quieter too, perhaps because it was always running full speed.
Refrigerator Main Control Board Assembly, AP4436216
One item to note, on the instructions it mentions “Eliminate thermistor wire in pin 2 of J1 connector”. It states this is only applicable to certain encoder models. As I wasn’t sure if they were referring to the board itself or the actual serial number of the fridge, I did a little research before clipping the wire. I found a serial number decoder table and once I saw the pattern realized and the instructions were for models manufactured from 10/02 to 09/03. Mine started with a DM (02/07) which made sense as I purchased it late in 2007. No need to cut the wire.
Hope this helps anyone with the howling freezer fan!