How to Prevent Ender 3 (Pro/V2) Thermal Runaway? (Detailed)

While 3D printing being widely available is fantastic for so many reasons, it can also be a game of troubleshooting at times that requires quite a decent amount of research and effort.

Even the Ender 3, one of the most popular 3D printers on the market right now, is not without problems. Out of everything that may go wrong while the Ender 3 is operating, a thermal runaway may be the worst thing that can happen.

Simply put, thermal runaway refers to the printer heating up to temperatures that are above safe levels due to faulty hardware. Issues related to thermistors and the heating cartridges are usually the culprit behind a thermal runaway, as these two parts work together to regulate the temperatures.

Due to the popularity of Ender 3 (Pro/V2), today, we will be talking about what you can do to prevent a possible thermal runaway on it in hopes of reaching as many 3D printing enthusiasts as possible.

So, how to prevent a thermal runaway on Ender 3 (Pro/V2)?

  • Activate thermal runaway protection on the firmware level, which allows the printer to power off if a thermal runaway is detected.
  • Maintain the thermistor, the heater cartridge, and the wires and connectors that connect these parts regularly.
  • Place your 3D printer in a secure area and keep it within eyesight while it’s operating.

Next up, we will be going into great detail about everything you can do to prevent a thermal runaway on your Ender 3, as a thermal runaway has a chance to produce catastrophic results, such as a fire if it takes place.

How to Prevent Ender 3 (Pro/V2) Thermal Runaway?

We will be talking about three things you can do to minimize the chance of experiencing a thermal runaway, and we highly recommend applying all three things to ensure safety.

Activate Thermal Runaway Protection

Thermal runaway protection is a feature that allows the printer to power down automatically if it detects a thermal runaway.

While the implementation may differ between different firmware, the general idea of how thermal runaway protection works is by comparing the temperature value of the thermistor with the expected value that it should have at that point.

In the case of a mismatch, the firmware powers the printer down and displays the thermal runaway error message on the screen.

To activate thermal runaway protection on your Ender 3 (Pro/V2), we recommend flashing the latest version of the Marlin firmware if you haven’t already.

According to the reports from the community, some versions of the stock Ender 3 (Pro/V2) firmware do NOT have this feature, which makes flashing the Marlin firmware the easiest and safest way.

As the Marlin firmware has thermal runaway protection enabled by default, you won’t need to perform further configuration in most cases.

Thermal runaway protection is certainly a life-saving feature for any 3D printer, including the Ender 3 (Pro/V2), which is why we highly recommend activating it as soon as possible if you haven’t already.

Maintain the Thermistor and the Heater Cartridge

The thermistor and the heater cartridge are two of the essential parts of a 3D printer, and they work together to control the temperature levels of parts such as the hot end and the heated bed.

As you may imagine, a problem with either of these parts can lead to a catastrophic failure caused by overheating, making it extremely important to ensure that they are functioning correctly.


The word thermistor is the combination of the words thermal and resistor. Simply put, a thermistor is a temperature sensor that reads the temperature levels of its surroundings.

Thermistors reside in the areas of the Ender 3 where temperature readings are required, such as the hot end and the heated bed, as the printer requires this information to operate correctly.

For the most part, thermistor maintenance involves ensuring that the hot end thermistor is sitting tightly in its place right next to the heating cartridge in the center of the heating block, and the wires that connect it are intact.

As screws of the thermistor may loosen over time, it’s a good idea to regularly check on the thermistor and give the screws a tightening to keep things safe even if you aren’t experiencing problems.

Heater Cartridge

The heater cartridge is the tube-shaped component responsible for providing the heat that allows the printer to melt the filament and conduct the printing process.

This component is also located in the hot end, as the hot end is where the printer melts the filament and moves it through the nozzle.

Just like maintaining the thermistor, maintaining the heater cartridge is about ensuring that it’s tightly secured in its place next to the thermistor and that the wires connecting it are not damaged.

As the screws of the heater cartridge can also loosen over time, similar to the thermistor, you should check regularly check the position of the heater cartridge and tighten its screws to ensure that it’s locked in place.

Secure the Area and Watch Your 3D Printer

The last step of preventing a thermal runaway or reduce the issues it may cause is to secure the print area and keep an eye on your Ender 3 as it operates.

Securing the print area is mostly about keeping flammables, electronics, and anything that can catch fire away from your Ender 3, as it’s already a piece of equipment that runs very hot.

Alongside this, we highly recommend keeping a fire extinguisher next to your 3D printer for you to be able to intervene swiftly in the case of a fire.

In the worst-case scenario where a thermal runaway causes a fire, the absence of any flammables in the area and the presence of a fire extinguisher will drastically reduce the risk of further damage occurring.

Finally, remember to always keep your 3D printer within your view as it prints and power it down as soon as you feel that something is out of order.

Do NOT leave your printer unattended for extended amounts of time to be able to catch the signs of something going wrong and intervene in a timely fashion.

Does Ender 3 (Pro/V2) Have Thermal Runaway Protection?

While the Ender 3 (Pro/V2) does support thermal runaway protection, community feedback tells us that this feature isn’t active by default in some versions of the stock printer firmware.

The best way of ensuring that thermal runaway protection is enabled on your Ender 3 is to flash the latest version of the Marlin firmware, where it is active by default.

What Causes Thermal Runaway on Ender 3 (Pro/V2)?

The thermistor and the heater cartridge are the components that are responsible for regulating the temperature of the hot end, which means that the occurrence of a thermal runaway often points us towards a problem with either of these components.

Here is a list of things related to the heating cartridge and the thermistor that may cause thermal runaway on the Ender 3 and any other 3D printer.

  • The thermistor is faulty.
  • The thermistor is loosened and displaced.
  • The thermistor has fallen out of the heating block.
  • The heater cartridge is loosened and displaced.
  • The heater cartridge has fallen out of the heating block.
  • The wires of the thermistor are faulty, damaged, or disconnected.
  • The wires of the heater cartridge are faulty or damaged.

Is It Safe to Leave Ender 3 (Pro/V2) Running Overnight?

We are highly against leaving your Ender 3 or any other 3D printer unattended for extended periods.

Allowing the printer to operate unattended eliminates your chance of noticing the signs that something may be going wrong and create significant consequences (such as a house fire), as we have seen numerous times before.

The bottom line is that it’s certainly not safe to leave your Ender 3 (or any other 3D Printer) running overnight.

Wrapping Up

While a thermal runaway is a serious issue that can happen to your Ender 3 at any time, you can prevent it or at least minimize the damage caused by it if you take the necessary steps for safety.

To quickly recap, we highly recommend activating thermal runaway protection, ensuring that the thermistor and the heating cylinder are properly connected and seated, and finally, securing the print area and paying attention to your printer to reduce the risk of a thermal runaway.

Stay safe!