jeff is correct.
in my case, the timer that controlled the auto-defrost cycle had failed
causing ice buildup and cold air blockage to the refrigerator.
I have a mid-to-late 1990's Frigidaire FRS26ZGG Gallery Series side by
side freezer-refrigerator that quit working over the weekend when we
were out of town (of course). We cleaned up the mess and opened up the
back to look things over. We cleared out the dust and dirt from the
coils, fan, and compressor and plugged it in again. The lights turn on
and the inside freezer fan and fan unit on the bottom back work and
compressor gets hot. The ice machine makes ice and the freezer is
working fine. The refrigerator got down to 38 degrees for a day or two
and the bottom back fan would shut off. Now it only gets down to 60
degrees and the bottom fan runs continuously. What is wrong and is this
an easy fix?