If your fridge is not cooling down to the right temperature, it may need a replacement thermostat. A good way to test a thermostat's functioning is to adjust the temperature so that it is slightly cooler. If the thermostat is working properly, this minor adjustment will start the compressor as the refrigerator cools down to your new setting. Check the inside of the refrigerator again after several hours to see if the thermostat was able to hold a constant temperature. If not, you can replace the thermostat by following this guide.
Unplug the refrigerator before removing any panels or screws. If the plug is hidden behind cabinets or in another hard-to-reach location, you can flip the breaker switch that controls the power to the kitchen.
Locate the thermostat on your fridge. For most refrigerators with the freezer on top, the thermostat is either at the rear of the freezer compartment or on the underside of the refrigerator's floor panel. In a side-by-side fridge, the thermostat will be located in the back, on the freezer side.
Remove the icemaker and any food or shelves located in front of the thermostat. Depending on the construction of your refrigerator, you may have to loosen a few screws or remove some retaining clips to take out the inside panel of the freezer.
Use needle-nose pliers to remove the wires from the ends of the thermostat's terminals. Grip the wires close to the end and gently tug until the slip-on connectors pull away from the terminal. Do not pull from the middle of the wires because they are thin and can break easily.
Remove any screws or clamps holding the thermostat in place. Some refrigerator models have the thermostat clamped around the evaporator tube, so be careful not to damage this tube while loosening the thermostat. Others may have a clip that can be released before pulling the thermostat up and out of the assembly.
Set the new thermostat in place and reconnect any clips, clamps or screws. If you had to unclamp the thermostat from the fridge's evaporator tube in the previous step, be sure to clamp the new thermostat in the same location. Slip the ends of the wires onto the terminals of the new thermostat. Replace any inside panels, screws or clips that you removed. Plug the refrigerator's cord back into the electrical socket or flip the breaker back on, and wait for the unit to cool down.
Before replacing the thermostat, thoroughly inspect your fridge to check for any other problems that may be causing temperature irregularities. Make sure the condenser coils on the rear of the fridge are clean and have plenty of ventilation. Use the hose attachment of your vacuum to clear out any dust or debris that has accumulated behind the refrigerator. Position the fridge so that there is at least a 3-inch space between it and any walls or cabinets.