Anyone who owns a dishwasher may experience a blown thermal fuse from time to time. That’s not unusual, and replacing it is a reasonably straightforward process.
But what happens if the thermal fuse keeps blowing again and again? If that’s the case, then you might have a problem elsewhere in the appliance.
Your dishwasher keeps blowing the thermal fuse (or high-limit thermostat) because it might have a broken wire, a problem with the wire harness, loose electrical connections (most common), water is too hot, or a faulty temperature sensor.
In this article, we’re going to explore all of these possible reasons to help you understand what’s going on. Then, we’ll look at how to fix each of these problems.
What Is A Dishwasher Thermal Fuse?
Firstly, it’s essential to understand the thermal fuse in your dishwasher and how it functions. Like any other type of fuse, a dishwasher thermal fuse is known as a ‘sacrificial device’.
Unlike other types of fuses, though, a thermal fuse reacts to excessive heat.
For example, if there’s a short circuit in the dishwasher, the fuse will heat up and blow when it reaches a specific temperature.
In simple terms, the fuse stops working or ‘blows’ to break the electrical circuit and protect the rest of the appliance from further damage.
In doing so, the thermal fuse also protects you from suffering an injury as you use the appliance.
Now, let’s look at what might be causing your thermal fuses to blow even after you’ve replaced them with a brand new one.
Keep in mind: in the dishwasher, might be 2 types of thermal fuses. One of them (it’s also called a high-limit thermostat) connected to the bottom of the tub and the second one located on the control board. Each of them serves a similar purpose.
Depends on the issues you have with your dishwasher, this article will help you to identify possible causes.
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Why Does The Dishwasher Keep Blowing The Thermal Fuse?
As mentioned earlier, several causes can lead to a thermal fuse blowing repeatedly.
They include a broken wire, a problematic wire harness, loose electrical connections, or even a problem with the machine’s pressure switch.
What it is: Just like any electrical home appliance, your dishwasher will have plenty of wires running throughout the machine.
Typically, these wires are kept out of sight behind panels that must be removed before you can access and inspect them.
The exact placement of those wires may differ slightly depending on the way your particular model was designed.
Usually, they’ll be behind the panels at the bottom or the rear of the dishwasher.
To be sure, please refer to the user manual or technical sheet that comes with the machine.
Those documents usually have diagrams that help you locate and identify the wires in your dishwasher.
Why it fails: Despite being insulated or coated, wires can sometimes break for several different reasons.
The wire could be of low quality, or perhaps a part of the wire suffered some kind of impact that was strong enough to break it.
A broken wire may come into contact with other exposed wiring or the metallic parts of the dishwasher.
That can lead to a short circuit, which causes the thermal fuse to heat up to the point that it cuts the circuit to protect the rest of the machine.
How to fix: First and foremost, always disconnect the dishwasher from the power supply and drain the water from the appliance.
Fixing a broken wire is very straightforward. The difficult part is locating the broken wire in the first place.
That will require a careful and up-close inspection of every bit of wire throughout the machine.
Once you’ve found the broken wire, all you have to do is cut and splice the wire together using a wire nut.
As a precaution, it would be wise to look out for any additional broken wires at the same time.
What it is: When replacing the thermal fuse, some manufacturers will also recommend changing the wire harness as well.
To put it simply, a wire harness is a bundle of wires that are used inside the dishwasher. Think of it as a complete set of wires prepared at ideal lengths to fit your dishwasher perfectly.
So, rather than trying to inspect and fix individual wires, wire harnesses make it much more convenient to replace the entire set of wires altogether.
Why it fails: Some manufacturers recommend changing the wire harness if you’ve changed the thermal fuse more than once.
One of the wires in the harness may be broken, burnt, or suffered some other kind of damage that could lead to overheating and a blown thermal fuse.
On top of that, exposed wires inside the harness may come into contact with each other, leading to a short circuit.
Replacing the wire harness may involve a little bit high cost, but it’s also a much simpler solution.
How to fix: Again, this bears repeating: be sure to disconnect the dishwasher from its power supply and drain any water inside.
Once that’s done, you can remove the panels, giving you access to the existing wire harness.
The tricky part about replacing the wire harness is connecting everything back correctly.
To do this properly, you’ll want to make sure that you have the user manual or tech sheets to guide you through the process.
Besides that, it would also help take photos of the older wire harness before removing it.
That way, you’ll have a photo reference to guide you in reinstalling the new wire harness.
What it is: As mentioned before, a dishwasher has plenty of electrical wires inside that connect each of its components together.
It’s crucial that each of those electrical connections are on tight.
Firstly, so that the dishwasher can deliver power to each component at the correct stage in the washing cycle.
Besides that, those connections must be put on tight to ensure that the electrical current can flow through without any restrictions, preventing problems like short circuits or excessive heat.
Why it fails: Having a loose connection inside the dishwasher means that the wires only make contact part of the time, rather than doing so continuously.
That can lead to an increase in the circuit’s amperage, and that will eventually cause the thermal fuse to overheat and blow.
How to fix: Firstly, refer to the user manual or tech sheet. Those documents will have diagrams showing you all of the wiring and connections that exist inside your dishwasher.
With that information in hand, it’ll be much easier for you to inspect each and every one to ensure that the connections are tight as they should be.
Faulty Temperature Sensor
What it is: Hot water is one of the most important elements when it comes to dishwashing.
That’s because the water needs to be hot enough to effectively remove dirt and grease from the items you put inside the appliance.
For that to happen, the dishwasher relies on a temperature sensor.
Suppose that the temperature sensor thermostat detects that the water coming in from the inlet is too cold.
If that’s the case, then the component will trigger the machine to heat the water up to a more suitable temperature.
When the water is hot enough, a working temperature sensor will stop the appliance from heating the water any further to avoid overheating and damaging the machine’s items.
Why it fails: Just like any other component in a dishwasher, the temperature sensor is prone to failure at some point.
The component itself could be faulty, or it could have suffered from too much wear and tear after many years in use.
When a temperature sensor fails, it may falsely sense that the water is too cold.
The dishwasher will heat up the water to the point that it overheats and blows the thermal fuse inside.
That’s another example of the importance of the thermal fuse: it blows to break the circuit.
Doing so will protect the dishwasher from further damage and prevent any injury from happening to the person operating the appliance.
How to fix: For the best results, it’s always a good idea to identify the correct replacement part first.
That will save you the trouble of accidentally buying an incompatible part. To do that, always refer to the user manual, technical sheet, or contact the manufacturer to find the correct part number.
With that part number, you’ll have a much easier time searching for a replacement part from the manufacturer or third-party parts sellers.
Replacing the temperature sensor will require accessing the inner components of the dishwasher because it’s typically located at the base of the machine.
So, be sure to disconnect the power supply to the machine before handling it. Then, you’ll need to drain all of the water out of the appliance.
It’s always best to refer to the user manual or technical sheet to understand where the temperature sensor is located. That will make it much easier to navigate around the different components to identify the temperature sensor.
Remove the connectors to the temperature sensor and replace it with the new one, connecting it in the exact same way as the previous one.