what is wrong with my samsung american f/f rs20ccms?

I have the exact same model as you. After 3 years of ownership it all went wrong. I would never ever buy this model again. It has a common fault which Samsung refuse to admit to. There is a sensor which controls the temperature that will need replacing. For a short term fix what you can do is defrost freezer for 24 hours (meaning you will lose your food which I did) and it will work again but this is for a very short time 3 weeks max. I did in the end call a Samsung Engineer who was recommended by Samsung who was reasonable and the problem cost around £30 plus call out charge. This was about two years ago so I unfortunately do not have the number still. I just stumbled across your question as I need to change a light bulb that has gone on ours now and felt I must answer you as I know what a nightmare this problem is and had not help or understanding. I hope this helps.

Helena Tremain
August 2010