For food safety, 40 degrees Fahrenheit is a magic number. Bacteria tend to grow easily above this temperature, while their growth slows considerably below this temperature. This makes food storage possible for several days assuming the refrigerator is between 40 and the freezing point of 32 degrees. If your refrigerator will not get below 40 degrees, however, it is not a safe place to store your food. The appliance has a problem that you can likely trace to one of a few origins within the refrigerator.
When the cooling coil inside the refrigerator's freezer compartment ices over it can restrict airflow and potentially interfere with the fan functions. This can prevent the refrigerator from getting as cool as it is supposed to and can pose a risk to your fresh food. Most modern refrigerators have a self-defrosting system that will keep the frost from building up on the coil, but it is possible for one or more parts of the automatic defrost to fail and allow this ice buildup. The defrost timer, heater or bi-metal switch could be the problem.
Dirty Condenser Coils
The condenser coil is usually located at the bottom or on the back of a refrigerator. This coil is the tubing in which the refrigerant leaves the cool part of your refrigerator and condenses the gaseous refrigerant back into liquid and flows through the compressor where it heats back up and transfers the heat into the air around the refrigerator. These exterior coils often gather dust and lint and become quite dirty. If you do not clean them on a regular basis, it can affect how well the refrigerator cools. You may use a brush or vacuum to clean these coils to make them operate at peak efficiency. Make sure you unplug the refrigerator before doing this kind of cleaning.
Occasionally the main problem with cooling in a refrigerator is the door gaskets. Weak, torn or otherwise damaged gasket seals around the refrigerator or freezer door let cool air escape freely to the outside. The refrigerator has to work much harder to keep up with the cooling demands and the temperature internally may never drop below 40 degrees. This can also result in condensation buildup on the interior walls of the unit.
Sometimes the answer to your refrigerator problem is so obvious that you forget to check it. The thermostat is the lever, knob or button that lets you control how cold you want the refrigerator to be. It's possible this setting is simply too high. If you adjust the thermostat down a bit and then use a thermometer to measure the actual temperature inside after leaving the door shut for a few minutes you may find that no additional attention to the refrigerator is required.