The refrigerator-freezer temperature controls the operating temperatures of both the freezer and refrigerator compartments. The temperature control switch also controls the on-and-off cycling of the refrigerator's motor compressor, and in some older refrigerators, it also controls the defrosting system. The temperature control may be the cause of a motor compressor running continuously or not starting at all. The temperature control also may be the problem if the refrigerator and freezer do not get cold enough, or if they get too cold.
Place one of the thermometers in the freezer compartment; place the other thermometer in the refrigerator compartment. Adjust the refrigerator-freezer control to a setting between "4" and "5" on its dial. With this setting, the motor compressor should cycle off when the freezer compartment reaches the EPA-recommended temperature of 3 degrees Fahrenheit, and the refrigerator compartment reaches the EPA-recommended temperature of 37 degrees Fahrenheit. If you have to adjust the thermostat switch to higher than a "6" to reach these temperatures. or lower than a "3" to maintain these temperatures, the thermostatic control is bad and needs to be replaced.
Move the refrigerator away from the wall and unplug it from its wall receptacle. If the refrigerator does not start, or continues to run, causing the food in the refrigerator compartment as well as the freezer compartment to freeze, you need to check for continuity through the thermostatic switch's internal contacts with a digital multimeter or continuity tester.
Locate the thermostatic control switch, which can be identified by a knob with numbers from "0" to "9" imprinted on it. In most cases, this control is located on the left, inside side wall of the refrigerator. In some cases, the control may be located at the top center of the refrigerator compartment. In either case, pull the control knob from the shaft and remove the screws holding the switch assembly in place. Pull the switch out and carefully disconnect the wires from the switch's terminals, securing them so they do not slip inside the wall opening. In most case, the wires are connected with push-on terminals.
Adjust the function switch on the digital multimeter to the R x 1 scale and attach the probes to the two terminals on the switch. With the switch's shaft turned completely counterclockwise to the "0" setting on the switch, the meter's LCD should display an “O.L.,” indicating no continuity if the switch is good. As soon as you start to advance the switch in a clockwise direction, the display should switch from the “O.L.” to a display of “0.000,” indicating continuity if the switch is good. If the meter displays a constant “O.L.” or “0.000”, the switch is defective and needs to be replaced.