[Renatefry]

My just over 1 year old upright freezer is no longer keeping its contents frozen, and it makes a loud continuous humming sound. I noticed that the door had been left cracked open (about an inch) for about 6 hours, which explains why certain item inside thawed. I increased the freezer temp control knob to the highest (fast freeze )setting, but colder air is not coming out.

[denman]

Here are your parts
Parts for Whirlpool EV188NYWS00 Freezer - AppliancePartsPros.com

You will have to find out what is humming?

It could be that the door being open caused excessive frost build up and perhaps the fan is jammed with ice, so it cannot start and therefore just hums.
If this is the case it is probably best to do a manual defrost to clear out all the ice/frost. Also dry the motor with a hair dryer to get any moisture out of the bearings etc. so that it cannot freeze and cause the motor to stall.

Check the compressor. If it is overly hot unplug the unit and let it cool down.
Then plug it back in and see if the unit operates OK.