My name is ***** ***** I am an authorized Whirlpool service technician and I can help you today.
If you are starting to see the frost in the back of the machine and it is now starting to affect the temp then you are experiencing a defrost failure.
Put simply you will either have to empty the freezer cabinet and defrost it by yourself with a hair dryer for about an hour. Or unplug the machine for 2 days to allow it time to defrost on its own.
Usually the first choice is better. Especially if you dont have another ref to keep all your food cold for the two days.
What you want to do is take that hair dryer and fan the hot air all around the rear inside wall of the freezer for the hour or so.
This will ensure the evaporator is properly defrosted and will allow the cold air to be circulated to the ref cabinet again. Thus allowing the machine to cool properly.
Then just set the ref temp to their normal settings and allow it to cool for two days. then monitor it from there.
If after a week you start to see the frost building up again get back to me here and I will tell you what you will need to do next.
But I am sure that the initial defrost will be enough.
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Thanks and please let me know how you make out.