While there are several reasons a refrigerator does not stay cold, one of the most common is the plug coming out of the wall outlet, according to The Family Handyman. If the lights are on in the refrigerator, it is receiving power. If they are not on, the plug should be checked by moving the refrigerator away from the wall.
If someone accidentally sets the thermostat to a warmer position or to the off setting, the temperature inside the refrigerator increases. Turning it back to the normal setting fixes the problem.
Overloading the freezer with boxes of frozen food to the point they block the vents prevents air circulation from the freezer to the refrigerator. If the vents are blocked, the freezer remains cold, but the refrigerator stays warm. The problem is easy to remedy by removing some of the boxes.
Refrigerators have heat exchange coils on the back or underneath the main body. These coils sometimes fill with dust and dirt, resulting in poor cooling. A vacuum works to gently clear them. On models with coils underneath, it is possible for something to stop the fan from turning due to debris accumulation. Owners should clean the fan and attempt to turn it by hand. Once the refrigerator has power, the fan should turn on its own. If not, the fan needs to be replaced.