My fridge will work fine and then next thing I know the fan in the freezer compartment is blowing but everything is melting (ice cubes etc.) I have pulled it away from the wall and noticed the fan by the compressor is running but the compresor is not. There is service panel on the upper corner behind the freezer area and when I give it a "Rap" with my hand I can hear the compressor kick in, usually it will stay on but sometimes it kicks on for a few seconds and then shuts off. But it almost always kicks in and stays on. Untill the next time it acts up which is every other day roughly. The other thing I have noticed is that the fan volume and the sound of the fan is much louder in the freezer when this is happening. When it seems to be working properly the fan volume is lower and quieter. When the freezer is in defrost mode does than fan volume increase? If thats the case then I think the sensor for the defrost is faulty. and what sensor or switch would respond to giving a "rap" with my hand to activate it? Thank You

The Mother board looks fine, the more I look into this the more I think the auto defrost is kicking in too frequent and too long, there is a difference in how the fan sounds when everything starts to melt in the freezer -vs- when it is working properly, in addition the length of time it takes to go from frozen to totally melted in the freezer is too fast to simply be melting from not cooling, it must be kicking the defrost heater.
KRSOLO

I put a thermometer against the back wall of the freezer and it got down to about 3 below zero. and the fridgerator is at 40 degrees.
(from my prior note about thinking its the defroster system kicking in the defroster heater for too long causing a quick melt down and melts things very fast, instead could it be that occasionally something is not triggering the compressor to kick in and the system is trying to cool down the freezer so the fan is on full blast without the compressor running. Could the fan on full a cause a fast melt down even without the defrost heater on?

The last time it acted up the circulating fan in the freezer compartment was on full blast and the condensor fan was running but the compressor was not. In fact I had taken everything apart on friday couldnt see any problems, put it back together and it worked great all weekend till last night I noticed the freezer temp went from 3 below to 30 degrees and this morning the temp was up to 40 degrees adn everything was melted again. I banged my hand against the side of teh fridgerator next to where the motherboard is and I heard the compressor kick in. As in my prior notes I have mentioned that when its acting up I have gave it a "whack" and the compressor almost always will kick in. Sometimes it will stay on for just a few seconds and turn off again, sometimes it will kick in and stay on and run like it should. On the rare occasion that it doesn't kick in I have unplugged it for awhile and then plugged it in again and then it seems to work for awhile. Could something be overheating on the motherboard or like you mentioned before is there a loose solder connection that is causing intermediate function? I have pulled the motherboard and everything appeared ok. Is there a relay for the compressor on the motherboard that is shot?

Thank you very much for the repair advice, I did replace the mother board and that repaired the problem, Thank you again, you guys do a great job!!