2002 Kenmore 160.61 Refrig / freezer (top)

Question

The fan in the freezer has stopped running. A look shows that
everything appears in working order; other then the fan which also
blows the cooler air into the lower unit. Could it be the fan or
the defrost timer. A look at the defrost timer shows that it is running
via a plastic wheel viewable by a clear plastic cover.