Can a freezer stop working, but the fridge still works?
If your freezer stops cooling but the refrigerator compartment works, the freezer may have frost build-up or clogged venting preventing it from doing its job. Check the venting in the back of the freezer to make sure no items are resting against it, then examine the ice build-up inside the freezer.
If your freezer is frosted over, ice may be freezing against the evaporator coils and obstructing proper airflow in the freezer. A faulty defrost timer may also be the cause of a freezer that continually frosts over.