1. Disconnect the power source.
2. Remove the control knob(s) by pulling it (them) off.
3. Remove the control panel.
4. Using a screwdriver (or nutdriver) remove the screws holding the thermostat. Do not damage the thermostat bulb and very gently pull the bulb from where it is seated.
5. Disconnect every wire from the thermostat.
6. Set the ohm meter on the RX1 scale and turn the thermostat to its warmest setting.
7. While holding the thermostat bulb in your hand for about 2 minutes, touch the two ohm meter probes to the two thermostat terminals. You should get a 0 reading on the meter. If not, the thermostat is bad and should be replaced.
8. Turn the thermostat to the off position and touch the probes again to the two terminals. You should get an open circuit reading. If not, the thermostat must be replaced.
9. Turn the thermostat to its mid position and put the thermostat bulb in a mixture of crushed ice and a little water for about 3 minutes while touching the ohm meter probes to the two thermostat terminals. The indicator needle should move from 0 to an open circuit reading. If not, the thermostat must be replaced.
Thermostats used in residential units are installed in the fresh food or freezer compartment while the sensing bulb is attached to the evaporator coil. There are occasions when the sensing bulb is routed through a maze of holes in the cabinet making it appear impossible to replace once the original one is removed. There is a way to make this job much easier. When all the screws securing the defective thermostat, sensing bulb and/or sensing bulb line are removed, tie a piece of strong cord (a few feet longer than the sensing bulb line) securely to the sensing bulb. Pull out the old thermostat and its bulb from the other end and the cord will follow. When the old line is removed, remove the cord from the old bulb and tie it to the new one. With the new sensing bulb line carefully straightened, pull the new bulb through with the cord and replace the screws securing the thermostat and its bulb.