If you remove the back wall inside the freezer and find that the evaporator coils have ice builtup on them, this usually indicates a defrost problem (defrost heater and thermostat or defrost timer (or adaptive defrost control on newer models)).
If the evap. coils are more or less clean, then it's probably the air diffuser (also called damper control). The diffuser is located between the freezer and the refrigerator sections.
I would recommend checking the evaporator coils first. Let us know what you found.
- jtrichards, please double check your model number. It doesn't come up at all.
- troy, please post your model number.
- dshaw01, diffuser is
#13 on this diagram and you can see
price and photos here.
- tottalyoff, please pots your model number.