Testing A Refrigerator Temperature Control Thermostat

To successfully preserve your perishable food items and keep your beverages chilled, your refrigerator needs to maintain the appropriate temperature, both in the refrigerator and freezer compartments. If the temperature inside those compartments is too warm or too cold, a malfunctioning temperature control could be the cause.

What is the appropriate temperature for your refrigerator?

What’s an appropriate temperature for your refrigerator to maintain? Repair Clinic recommends the refrigerator compartment temperature be kept between 35° F and 40° F (2° C to 4° C) for the appliance to work optimally. What about the freezer compartment? That temperature should be kept at 0° F ( -18° C) or lower.

If you have an older-model refrigerator that uses a thermostat switch and sensing bulb assembly to monitor and control the air temperature inside the appliance, you can test the thermostat to help determine if the part is functioning properly. Before we get to that, let’s review how the temperature control works and how the component will vary depending on the model.

How the temperature control works

The air temperature in both the refrigerator and freezer compartments is regulated by the temperature control. This device senses the changes in the air temperature and will send voltage to the necessary components in the cooling system in order to lower the air temperature or shut off that voltage when the air temperature has reached the appropriate level.

The two types of temperature controls

Depending on the refrigerator model, there are two types of temperature controls: older or smaller refrigerators will use a mechanical thermostat switch and sensing bulb assembly; more recent models will use an electronic control board that works with one or more sensors. While many refrigerators have one control located in the refrigerator compartment to control the temperature in both the refrigerator and freezer compartments, some models will use a separate control to set the temperature in the freezer.

The temperature control allows voltage to travel to the compressor and fan motors

When the thermostat switch’s sensing bulb, or the control board’s sensors, detect that the air temperature in the appliance has risen above a certain level, the refrigerator control will allow voltage to travel to the compressor as well as to the condenser fan motor and the evaporator fan motor. When cycled on, the compressor pumps refrigerant in gas form into the condenser coils where the gas is then condensed into a hot liquid. The condenser coils dissipate the heat as the liquid travels through them which is assisted by the condenser fan motor blowing air across the coils. The refrigerant is then pumped into the evaporator coils where it expands back into a gas. This makes the coils cold. The evaporator fan motor draws air over the cold evaporator coils which chill the air before that air is circulated through the freezer and refrigerator compartments.

Once the air temperature in the compartments is cold enough, the temperature control shuts off the voltage to the cooling system. Keep in mind that it’s normal for the temperature to vary throughout this cycle.

Troubleshooting a refrigerator temperature control thermostat

A malfunctioning temperature control can prevent the cooling system from cycling on, resulting in the temperature in the appliance being too warm, or cause the compressor to run too often which can make the refrigerator compartment too cold, potentially freezing your food items. If the temperature control is a thermostat switch and sensing bulb assembly, here are the troubleshooting steps you can take to determine if the temperature control thermostat is functioning properly:

Listen for a “click”

  • The first step is to manually rotate the thermostat dial to “call” for more cooling.
  • After the compressor has cycled on, slowly rotate the dial to its lowest setting (less cooling) and listen for a “click”. That clicking sound will indicate the cooling system is shutting off and the thermostat is working.
  • If you don’t hear a clicking sound or are unable to successfully cycle the cooling system on, you can use a multimeter and ice water to test the temperature control thermostat for electrical continuity – a continuous electrical path present in the part.

Testing the temperature control thermostat for electrical continuity

  • If using an analog multimeter, be sure to properly calibrate the meter first by pinching the red and black leads together while adjusting the meter needle to “zero”. For both analog and digital multimeters, rotate the range selection dial to the lowest setting for ohms of resistance.
  • Place the thermostat’s sensing bulb in the ice water.
  • Contact the black and red multimeter leads to the thermostat terminals. Inserting the metal ends of the leads into alligator clips and attaching the alligator clips to the terminals will free your hands for the next step.
  • Rotate the thermostat dial. As the dial reaches a lower setting, the electrical continuity in the thermostat should be interrupted.
  • If the thermostat tests “negative” for electrical continuity at all dial settings, or “positive” for continuity at all settings, then it’s likely you’ve got a broken thermostat and it will need to be replaced with a new one.

Repair Clinic provides free refrigerator repair resources

As your repair partner, Repair Clinic has hundreds of free model-specific refrigerator repair videos, step-by-step guides, and schematics. Enter your refrigerator’s full model number in the Repair Clinic website’s “Videos & Articles” search bar to find detailed repair help for your appliance, including how to correctly install a new temperature control thermostat on a Frigidaire refrigerator (model FFTR1814TW8) and replace the damper control assembly in the model GSE25GSHPCSS GE refrigerator.

Use only genuine OEM refrigerator parts for all repairs

Regardless of the repair, Repair Clinic recommends using only genuine OEM parts for the best results and to extend the life of your appliances, lawn and garden equipment, and heating and cooling products. To find the exact original manufacturer part that fits your refrigerator, enter the full model number of the appliance in Repair Clinic’s “Search Parts Online & Get Answers” search bar for a complete list of compatible parts. You can then use the “Part Category” and “Part Title” navigation filters to narrow that list down to locate the specific refrigerator part you need, direct from such manufacturers as Samsung, Frigidaire, KitchenAid, GE, Kenmore, LG, Maytag, Whirlpool, among others.

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