Sounds like you have a defrosting problem, check in the freezer side to see if there is snow on the back wall, if there snow,there could be one of three things wrong. The timer , defrost thermostat[bi-metal] or heater.Some newer fridges have electronic boards to replace the timers. I would defrost the snow and check in the next few days to see if the snow comes back,if so check these part,s I just mentioned.