I have a Maytag Freezer model MQU2057AEW that is not cooling on the top racks while it is even freezing water in a cup in the bottom tray. I opened the back panel and found that the fan is not operating. Compressor is humming along non-stop. Question is what is the use of that fan in the back panel?

Thanks for your response, and I would appreciate if you could further clarify with more info: normally does the fan would operate continuously, or would it turn on during the cooling cycle and turn off during defrost cycle? The reason I am asking is because the fan could be good but it might not have been activated because it could still be in defrost cycle? However, if the fan operates continuously regardless of which cycle the freezer is in, then it is easy in my case to conclude that it is gone bad and needs replacement. Thanks.