Thermal fuse is an essential part of refrigerator if it’s not working it can cause a lot of problems inside your refrigerator . It ensures that heater element inside the freezer wont cause any fire hazard . Since , It blows as the temperature increased to the rated value. These thermal fuses are non-reusable components which means you need to replace it once its burned . There are several different types of thermal fuses available . If you are replacing a thermal fuse here are the things you need to know.
Working Principle of Thermal Fuse
When talking about working principles of thermal fuse there are two types of thermal fuse types. These two different types of thermal fuses have different type of working principles. These different types of thermal fuses have different thermal and electrical characteristics .Even though , the working principles and characteristics are different , the function of these thermal fuses remains the same.
Type 1 – ( SW-1, SW-3, SW-5 series thermal fuses )
As you can see in the cross section diagram. Inside of this type thermal fuses there are few components a sliding contact , a spring that pushes against a non-conductive thermal material (solid) . The current flows through the sliding contact into the outer metal layer then to the lead in the other side. However, As the temperature reach the rated value this non-conductive thermal material will become a liquid. This allows the spring tension to push the sliding contact . Thus , Breaking the current flow (Open Circuit).
Type 2 – ( SW-2 series thermal fuses )
As you can see in the cross section diagram .The two leads of this thermal fuse are connected by a special metal component . This metal component will break at a set temperature . To increase the breaking action there is a resin compound which will also melt. To protect the components from oxidization inside the thermal fuse filled with epoxy material.
Testing the Thermal fuse
In order to test the thermal fuse you need to locate the wires that connects to the thermal fuse. Because , Both the thermal fuse and the thermal switch comes in the same package . Once you locate these wires then locate the pins of the connector that connected to these two wires. Put your multi meter in the continuity or diode mode and touch each pins of the connector with the probes of the multi meter. You should hear the Beep of your multi meter or If you are in diode mode it should show a value below 1 . This means that the thermostat is OK. If your multi meter doesn’t make any beep sound and in diode mode it shows “OL” (Open Loop) .This means that your thermal fuse is bad.
Causes of Bad Thermal Fuse
To know whether the thermal fuse is bad or not .There is a simple way.If your freezer have Ice build up , The thermal fuse can be the reason behind it .Because , If the current doesn’t flow through the thermal fuse the heater cant work .Thus , There is no way to melt the ice. There are few things that can cause not working thermal fuse. Here are some of them.
Burned Thermal fuse
As we have mentioned in the Testing Thermal Fuse section. If your multi meter doesn’t show values that we mentioned in that section , You may have a burned thermal fuse . The only way to fix this is by replacing it . Since , Most of the time the thermal fuse and the thermal switch comes in a single package you have to replace the whole unit . However , If you have a bad thermal fuse , you may have a [bad heater] too . Check whether you have a [bad heater] before replacing the thermal fuse.
The copper pins inside the connectors of your refrigerator is very venerable to corrosion and oxidization. Which creates layers of oxides in top of the copper pins. Thus, breaking the connection between pins.Which results open circuits.
Fix – Unplug and Clean thermal fuse connector pins using a tooth brush soaked in Isopropyl Alcohol or spray contact cleaner and brush the pins with tooth brush. Then , plug it back .
There are mainly two types of thermal fuses . Each of these types have different working principles and different internal components . You can check your thermal fuse using a multi-meter in the continuity mode or diode mode. There are several causes that can cause non functioning thermal fuse . If your thermal fuse burned , you need to check whether your heater is good or not. Replace the thermal fuse with a one with the same ratings . If the thermal fuse and the thermal switch comes in a single package , You have to replace the whole package . Because , In order to replace the thermal fuse in a such a package ,you have to break the seal in order to replace it.