There are various reason why your freezer could be working nice and frozen, while your fridge area is warm with no cold air. Common reasons and solutions are explained below:
1. Check to see that your freezer is not over packed and filled, not allowing any air flow inside the freezer. How the refrigerator system works is that first it cools the freezer compartment. Then the cold air is drawn from the freezer compartment into the fridge compartment below through a chamber using the evaporator fan located behind the freezer compartment. In an over packed freezer, the cold air just cannot be sucked through into the fridge compartment area. Try removing some frozen stuff from your freezer and allow the cold air to circulate easily.
2. Check to see that your evaporator fan is working properly. With a defective evaporator fan, the cold air from the freezer cannot be pulled into the fridge compartment. When this happens, the freezer compartment will become too cold frozen and the below fridge compartment will be warm. Solution is to replace the evaporator fan. Listen for the evaporator fan to hear if it runs. If not, then this fan has to be replaced with a new one.
3. Check to see if your evaporator coil has any frost on it. If it does have frost on it, this means that either your defrost heater assembly or your defrost thermostat is not working properly. They will need to be replaced. To test if this is the problem. Allow your freezer to be unplugged for about 12 hours, after which you plug it back in and see if the same problem happens again. If it does, then it means your defrost heater assembly or defrost thermostat is not working.
4. Check to see if your defrost timer is working or not. Defrost timer controls the cycle of cooling and defrosting for your fridge. If your defrost timer is spoiled, it may stay at one part of the cycle either cooling or defrosting. If it stays at cooling, then your fridge will cool non stop causing frost to build up at the evaporator coil and not allowing any cool air to circulate properly. If it stays at defrost cycle, the cooling will not happen and your freezer and fridge both will become warm. So you need a proper working defrost timer to control the cooling and defrosting cycle.
5. Check your damper control assembly. If this is broken or stuck, not enough cold air can pass through from the freezer compartment into the fridge compartment.