How to Tell If Your Defrost Thermostat is Bad? – Complete Guide

Are you having issues with your fridge and want to know how to tell if your defrost thermostat is bad?

Our full guide will help you with everything you need to know and the steps to fix it!

One of the most common refrigerator issues you’re going to face is going to be related to its defrost system. 

Once you start experiencing it, food spoilage can occur as quickly as 2 to 3 days.

One of the first things you’ll notice if you have a bad defrost thermostat is that your food starts to spoil earlier than expected. Whenever you check the temperatures, it’s usually warmer than your thermostat setting. Lastly, you want to check your condenser coils to check if it’s frozen over.

Let’s look at the different causes and symptoms of this particular issue so you can detect the problem early and take the necessary actions to fix it.

Let’s get to it!

Bad Defrost Thermostat Symptoms

If you have a bad defrost thermostat, you will see some tell-tale signs.

We recommend checking your fridge’s hardware since the likely cause will be from one of the components of the defrost system.

Here are some of the symptoms and causes of this problem with your refrigerator:

1. Defective Thermostat

A faulty thermostat can lower your fridge’s temperatures to unsafe levels. If spoilage occurs unusually earlier than expected, you know there’s something wrong with the thermostat.

2. Frozen Evaporator Coils

If your coils are frozen, your fridge will not be able to expel heat from inside efficiently.

Temperatures inside your refrigerator vary wildly; they can get too hot or too cold.

3. Faulty Defrost Timer

Your fridge’s defrost mode can malfunction and heat up much longer than usual. You’re going to see temperature fluctuations inside.

4. Defrost Heater Issues

Your defrost heater melts the frost that can build up inside your refrigerator. It can affect the temperatures inside your fridge and can cause more problems.

These are everything you need to know if your refrigerator has a faulty defrost thermostat.

Let’s now proceed with the steps on how you can confirm the issue and fix it!

How to Tell if Your Defrost Thermostat is Bad

The quickest way to tell if your defrost thermostat is bad is when you see frost building up inside your fridge.

The defrost system of modern refrigerators should be enough to stop this from happening.

Having a thick layer of ice inside your fridge can affect its efficiency and temperature levels.

If you see a thick layer of frost, you want to switch your fridge off and wait for it to melt completely.

Once it’s gone, you can wipe down the walls to remove the moisture and turn on your refrigerator. At this point, you’ll want to monitor if frost continues to build up after restarting it.

If it does, you’ll want to check out these other ways to tell if you need to fix your defrost thermostat:

Step #1: Is Your Food Spoiling Earlier than Expected

One of the ways you’re going to tell if your fridge has a bad defrost thermostat is that your food starts spoiling earlier.

A bad defrost thermostat means that your fridge cannot maintain the optimum temperatures for the stuff you’re storing.

It will likely be warmer than your set temperature, and food spoilage is one of the first things you’ll experience.

This is a symptom that will not have any visible signs, so you will have to rely on your other senses here.

Here’s what to do if your food starts spoiling earlier than expected:

1. Freeze meat, fish, butter, cheeses, berries, and others.
2. Freeze your leftovers.
3. Don’t overpack your fridge for better airflow.
4. Store items in an airtight container to avoid contamination.

Note: You also want to take note of the type of food spoilage you’re experiencing, as this will help when you attempt to fix the problem later on.

Step #2: Does Your Fridge Have Wild Temperature Fluctuations

The next thing you want to look out for is temperature fluctuations inside your fridge.

If there are times when your fridge is too cold, then warm the next time you open it. There’s something wrong with the defrost thermostat.

There are a few culprits if the temperature of your fridge is unstable. The most common one is your defrost thermostat, especially if you have a problem with the defrost timer and heater.

Here’s how to know if there are temperature fluctuations inside your fridge.

1. Set your refrigerator’s thermostat to your desired temperature.
2. Get a digital fridge thermometer and place it inside.
3. Wait for at least 30 minutes.
4. Check the reading on your thermometer if it matches your setting.

Note: Repeat this process as often as you want to know your fridge’s actual temperatures.

Step #3: Check Your Thermostat Setting

If you experience temperature issues, you want to check if you have set your thermostat properly.

If the thermostat of your refrigerator is located inside, it’s possible that you can accidentally touch it and change the setting to a much warmer one.

You’ll need to check it once in a while to confirm that it’s still set to the correct temperatures.

Here is the temperature you want to set your thermostat to:

1. The optimal temperature for storing food is below 40° F.
2. You can set it to as low as 37° F.
3. Your freezer should be set at 0° F.

Note: These temperatures will keep food fresh and prevent frost build-up on produce. It will also stop the growth of bacteria such as salmonella, E. coli, and others.

Step #4: Unplug Your Refrigerator to Stabilize Temperatures

If you continue to experience a wide range of temperature variations inside your refrigerator, you’ll want to turn it off and unplug it to reset its compressor.

The coolant may not be circulating properly, causing your fridge to be inefficient. Airflow can also be blocked, which can cause the same issue.

Here’s how to reset your fridge’s functions:

1. Transfer the contents of our fridge to coolers.
2. Unplug your refrigerator.
3. Move it away from the wall to improve airflow.
4. Wait for at least 12 to 24 hours.
5. Plug and turn your fridge back on.

Note: If the issues are temporary, like bad airflow or coolant not circulating properly, this step will fix your problem.

Step #5: Check Your Fridge’s Condenser Coils

If none of the steps work, the culprit is possibly frozen or dirty condenser coils.

This is one of the most common issues of a bad defrost thermostat and can cause your fridge to have variations in its temperature.

When was the last time you had the coils cleaned on your fridge? If your answer is never, we recommend checking and cleaning it.

You’ll want to know where the coils for your fridge are. Most models have them behind the grille, at the back, or on top of your fridge. 

The panels that cover it should be easy to remove so you can check if it’s frozen over or not.

Here’s how to check your refrigerator’s condenser coils:

1. Unplug your fridge from the socket.
2. Open the panels to gain access to the coils.
3. Check if it’s frozen or dirty.
4. You’ll need to wait until the ice fully melts if it’s frozen.
5. If it’s dirty, you can use a vacuum to clean it.

Note: You can also use a can of compressed air and a toothbrush to clean the coils.

If your refrigerator continues to have temperature variations, you can be sure that there is a hardware malfunction with the defrost thermostat.

You can call a technician and describe your observations in Steps #1 and #2. They’ll be able to help you successfully troubleshoot and fix your issue.

Read Next: How to Tell if Your Thermostat is Low Voltage?

Bottom Line

Now that you know how to tell if your thermostat is bad, you can try these steps out and see if you’re having issues with it.

You want this system on your refrigerator to work optimally since it will prolong the food inside and your equipment.