My friend told me to take the panel off on the inside freezer compartment and see if it was frozen over. It was, so I defrosted it with a hairdryer, and it worked great. Now it has happened again and it has only been 3 weeks since the last incident The model is # MSD2641KES only 2 years old. What else do I need to do?

You need to figure out which part of the auto defrost is not working. If you are familiar with taking off the freezer panel to defrost the evaporator I would start there. Remove the panel, defrost again and ohm out the defrost terminator and the heater. If both are OK your problem is in the timer. The dfrost terminator is normally closed and opens when warm, so you may have to put it into another freezer to check it (about 15 minutes).

This model has a ADC board which is located in the top control panel in the refrigerator section. Replace this and then replace the defrost (bi metal) thermostat that is located on top of evaporator, behind inside back panel of freezer. This should fix it. These ADC boards go bad frequently.
Rich
Western Appliance Repair of Boise
Western Appliance Repair of Boise 208-863-3702