During the automatic defrost cycle, you may notice a red glow in the vents on the back wall of your freezer compartment. This is normal during the defrost cycle.
This part of the normal defrost process occurs every 9-13 hours to maintain frost free operation. A small heater turns on for a few moments to melt any accumulated frost or ice from the freezer coils. The heater melts the frost, which drains down to a collection pan never the compressor assembly. The heat from the compressor operation evaporates the melted frost the next time the compressor turns on.