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Replacement parts for Whirlpool W8TXNGFWB00 REFRIGERATOR | AppliancePartsPros.com
Have you checked/cleaned the vents on the front kick plate and rear cover?
Same applies to the condenser coils.
Be sure to unplug the unit when doing this.
Is the compressor running? You can usually hear it but should also be able to feel it vibrating.
Is the condenser/compressor fan running when the compressor is running?
Is the evaporator/freezer fan running?
If compressor and fans are running all the time or most of the time, remove the cover in the freezer so you can inspect the evaporator coils.
If partially frosted, then it is probably a sealed system problem.
If heavily iced/frosted over then you have a defrost problem.