Damper Control Assembly
If the freezer is cold but refrigerator is warm the air damper control might be stuck closed or broken. The air damper control is either an automatic or manually operated door which opens and closes to let more or less cold air into the refrigerator compartment. If it doesn't open properly it won't let enough cold air into the refrigerator. If the evaporator fan is running, the damper door is open and no air is coming out. The evaporator may be frosted up caused by a defrost problem.