The thermostat controls a refrigerator's temperature by sensing temperature changes in the unit and prompting the compressor to turn on and off in response to those changes. The compressor consists of a pump and motor assembly which are housed in a sealed compartment through which the refrigerator cooling liquid travels. When a refrigerator loses its ability to cool evenly and accurately, a faulty thermostat might be the reason. You can test the thermostat along with following basic guidelines in order to help maintain proper temperatures in your refrigerator.
Set the ohmmeter to RX1 scale or to the lowest ohm scale.
On the right side of the meter, set the pointer to "zero," making sure the probe ends make contact with each other.
Put one probe on the left side of the thermostat and one on the right side of the thermostat.
The meter should not show a reading if the thermostat is turned off. If a reading appears, replace the thermostat. When the thermostat is turned on, the meter should indicate "0" ohm or .3 or .2 on a digital readout. If it does not appear as "0" ohm or .3 or .2, replace thermostat.
Turn the thermostat on and place each probe on either side of the thermostat so meter reads "0" ohm or .2 ohm digital. Put water and some ice in the cup. Temperature should be 0 degrees C. If, after four minutes, the meter does not reflect infinite or .0000 on the digital meter open circuit, replace the thermostat.
To prevent temperature reduction, avoid putting large quantities of warm foods into refrigerator. Vacuum dusty coils underneath the refrigerator to improve the cooling function of the unit. Ensure that the unit sits four inches from wall to allow cool air to circulate. Avoid opening the refrigerator and freezer doors frequently to preserve low temperatures.
If you must replace the thermostat, be sure to buy the exact model that came with your refrigerator. Always turn the power off and unplug the refrigerator before beginning any repairs.