My 22 year old frig is not maintaining freezer temperature overnight. During the day the frig temp is around 40F and the freezer between 0F and -10F. When I check it in the morning the frig temp is still close to 40F but the freezer temp has risen to close to 30F (i.e. a 40 degree rise). I've cleaned the coils but that hasn't made any difference. I haven't found any other posts on this forum that describe a similar problem. We're thrown out most of the food in the freezer just to be on the safe side.

I have the freezer temp control set to the coldest setting. Once I've checked the temperatures in the morning, the freezer will gradually cool down to 0F to -10F again in an hour or so.