A malfunctioning defrost thermostat may be the cause of your refrigerator’s uneven cooling or ice accumulation. This little but essential component makes sure that your refrigerator’s defrost system only turns on when needed, avoiding too much frost and preserving effective cooling.
In order to ascertain whether a refrigerator defrost thermostat requires cleaning, repair, or replacement, our appliance repair specialists describe in this article how to test it at home using simple instruments.

What Is a Refrigerator Defrost Thermostat?

The defrost heater in your refrigerator is turned on and off by a defrost thermostat. It keeps an eye on the evaporator coils’ temperature and turns on the heater when they become too cold, usually between –30°C and –45°C. To avoid overheating, the heater is turned off after the ice melts.
Frost may build up on the coils if this component fails, limiting ventilation and making your refrigerator work harder to maintain temperature.

Signs Your Defrost Thermostat Might Be Bad

Keep an eye out for these typical signs prior to testing:

• Your freezer’s rear panel has thick frost or ice buildup;
• The freezer compartment feels warm even though the freezer is too cold;
• The defrost cycle never activates or runs too frequently;
• The freezer hums or runs for extended periods of time;
• The temperature fluctuates even after you reset the thermostat.

It’s time to inspect yours defrost thermostat if any of these problems seem similar.

Tools You’ll Need

To check your thermostat accurately, you’ll need:

• Multimeter (to test for electrical continuity)
• Compressed air spray (for cooling simulation)
• Screwdriver (to remove access panels)

Step-by-Step Guide: How to Test Your Defrost Thermostat

1. Unplug the Refrigerator

Before working on your equipment, always turn off the electricity. Prioritize safety.

2. Locate the Defrost Thermostat

Behind the freezer panel, the thermostat is typically attached to or close to the evaporator coils. It is a tiny, circular piece of plastic or metal that has two wires attached to it.

3. Test at Room Temperature

Set your multimeter to the continuity or resistance mode.

• The thermostat should not exhibit continuity at normal temperature, indicating that the circuit is open.
• It is probably flawed if it exhibits continuity at this stage.

4. Cool Down the Thermostat

Now use your compressed air spray to imitate freezing temperatures. The liquid gas that emerges when you turn the can upside down and spray the thermostat for a few seconds will make it extremely cold.

• Check with your multimeter one more after it has iced.
• At this point, the thermostat ought to display continuity, signifying that the circuit is being closed as intended.

The thermostat isn’t working correctly if there is no continuity while it’s cold.

5. Check the Resistance

At room temperature, working defrost thermostats often read very high resistance (open circuit), and when it becomes cold, they drop to less than 100 ohms.
Consult the technical sheet or user manual for your refrigerator for the most precise figures.

When to Replace the Defrost Thermostat

It is preferable to replace the thermostat if it fails both tests. Worn or corroded electrical contacts;

• Moisture is seeping into the component.
• Extended exposure to high temperatures are common reason for failure.

Your refrigerator’s cooling efficiency can be increased and regular defrost cycles restored by replacing the thermostat.

Expert Tip

A malfunctioning defrost heater, control board, or sensor wiring could be the cause of your new thermostat’s short-term malfunctions. To avoid reoccurring issues, it is usually a good idea to have a technician inspect the complete defrost system.

Professional Refrigerator Repair Help

While testing a defrost thermostat is a simple do-it-yourself task, handling electrical components might be challenging. Our qualified specialists at Advance Appliance are here to assist you if you’re unsure or would like a professional diagnostic.
Whirlpool, GE, LG, Samsung, Kenmore, and Frigidaire are just a few of the major refrigerator brands that we fix.
Make an appointment for service right now, and let our professionals to restore optimal functionality to your refrigerator.

Key Takeaways

• The defrost thermostat regulates your fridge’s defrost cycle.
• Test it using a multimeter for continuity and resistance.
• It should be open at room temperature and closed when cold.
• Replace it if readings are off or the component looks corroded.

Professional help is available for safe and lasting repairs.