How to Solve Thermal Runaway: E1 Printer Halted on Ender 3

Did you just get the “Thermal Runaway: E1 Printer Halted” error on your Ender 3? If yes and you want to know how to fix the error then continue reading this article as I’ve covered all the things that might be causing the printer to halt and how to fix them.

Does not matter if you are experienced with electrical stuff or you are experienced in 3D printing, hearing a loud beep from your 3D printer is scary. When you check the screen of your Ender 3 to find out what is causing the loud beeping sound you are presented with the following error which does not make any sense at the beginning.

This picture shows the thermal runaway e1 error on Ender 3

It can be troublesome and daunting for new users to fix or resolve the above error by themselves without knowing the real cause of the error.

In this article not only I’ve given you the solutions to fix this, but also the causes of the error and precautions so that you know what you are exactly doing with your Ender 3 hardware and how to prevent the same error in the future.

What is Thermal Runaway?

Thermal runaway is a process that is accelerated by increased temperature, and in turn, the increase in temperature releases more energy which increases the temperature even more and the cycle continues.

When your printer is not able to stay at the configured temperature and keeps increasing you get a thermal runaway error. It is a good thing that your 3d printer has thermal runaway protection otherwise infinitely increasing temperature can cause fire to break out which may lead to catastrophic loss.

What Causes Thermal Runaway on Ender 3

  • Thermistor (99% times culprit)
    • Loose
    • Faulty
  • Heat Cartridge
    • Loose
    • Faulty
  • Power Supply
    • 115 or 230
    • Faulty
  • New Filament
  • New Hotend
  • Printing in room where temperature is fluctuating

How to Solve Thermal Runaway: E1 on Ender

PID Autotuning:

If you have changed your filament, hot end, cooling fan, or any major change that can affect the heating and cooling of the heat block or requires you to change the target temperature then you have to PID autotune your 3d printer.

If you have not done any of the above then you can jump to the next step!

PID(Proportional Integral Derivate) value is used by your 3d printer to keep the temperature at the target value without a sudden increase or decrease in temperature.

How to PID Autotune Ender 3

If your firmware supports PID autotuning… GREAT!, you saved yourself a few minutes and from a little bit of headache. Navigate the MENU in the following order to PID autotune:

Main>Configuration>Advanced Settings>Temprature>Pid Autotune E1

Turn the knob to change the target value, and set it to the value that you want your heat block(nozzle) to reach when printing. Once done your printer will start autotuning the PID values and it might take up to 10-15 minutes.

However, if your firmware doesn’t have a PID autotuning option then you have to manually PID tune your 3d printer.

Even after doing PID tuning, you hear that unpleasant beep sound and the error message pops up again “Thermal Runaway: E1”. Then it’s most likely the thermistor is causing the issue.

Fix Faulty Thermistor:

The thermistor is a component that changes its resistance based on temperature. It is used in 3d printers to calculate the temperature of the heat block. Often this is the real culprit behind the thermal runaway errors.

Even the thermistor can cause the issue because of one of the two reasons:

  1. Loose thermistor connection or dirty thermistor
  2. Faulty or Broken thermistor

Let’s look at how to solve each one of them.

Loose thermistor connection or dirty thermistor: 

Solving this is quite easy but you have to be very careful! Because the thermistor is a very fragile component that can break very easily.

Continuous heating and cooling of the heat block may cause the screw and thermistor to become loose over time because of thermal expansion. A loose or overly tight screw of your thermistor will cause thermal runaway errors.

Thermal paste is used when putting the thermistor into the heat block, just like it’s done with the CPU and its cooking fan when assembling a computer. Over time this thermal paste turns into a white residue which can cause thermal runaway errors.

Follow the steps to fix the loose thermistor connection and clean the dirty thermistor at the same time.

  1. Remove the screws that are holding the cooling fan to expose the hotend of the Ender 3. Now you will see two wire groups one is orange(Heater Cartridge) and the other is black(Thermistor).
  1. If you look carefully you will see the thermistor is hidden under a screw that is holding the wires of the thermistor. Carefully remove that screw as well.
  1. Gently pull out the thermistor from the hole and gently clean it making sure there is no white residue or dirt over it, blow out all the dirt from the hole where the thermistor is placed.
  1. At this point, check if your thermistor is damaged, you will be able to tell this by just looking at the thermistor itself. If it does look damaged then don’t even bother putting it back and testing it because it might short and cause damage to the thermistor connector port on the motherboard rendering it useless.
  1. If the thermistor and its wire look good to you and you have cleaned it properly along with the hole on the heat block. Then securely and gently place it in the same hole from where you have pulled it out, don’t push it.
  1. Now put back the screw above the thermistor and wrap the wires around the screw just the way it was. Slowly tighten the screw be careful to not over-tighten it as it will cause damage to your thermistor.

In most cases cleaning and reinstalling the thermistor will solve the issue, if it doesn’t then you need to replace your thermistor. 

Luckily thermistors are very cheap and are available online, you can easily buy thermistors on Amazon and follow with the next step.

Faulty or Broken thermistor

Broken thermistors don’t only come with the thermal runaway error but they can also short and do permanent damage to your printer’s motherboard if the motherboard doesn’t have protection against it.

Replacing the thermistor is just as easy as reinstalling it just like the above step, it’s just more time-consuming than simply reinstalling a working thermistor.

Steps to Replace a broken thermistor:

  1. Follow the above 3 steps to take out the broken thermistor if not already.
  1. Remove the old thermistor by cutting it from the wire. Now strip off the ends of the wire to expose the inside of the wire which will be used to connect the new thermistor.
  1. Put on the joining sleeves and connect the new thermistor with the exposed wires.
  1. Now slowly heat the joining sleeve so that it properly connects and joins the thermistor with wires. Make sure to not supply too much or high temperature of heat because it might melt the sleeve and damage the wires.
  1. Once the new thermistor is connected to the wires, put back the thermistor into its place in the heat block. Don’t push it just place it.
  1. Now put back the screw over the thermistor, and wrap the wires around the screw in the same fashion as it was when you took it apart. Now slowly tighten the screw, don’t over-tighten it because it will damage the thermistor and its wires.

Now you should be able to print successfully without facing the “Thermal Runaway: E1” error.

Tips to Avoid Thermal Runaway E1 Error on Ender 3

  1. Make sure your printer’s power supply is set to its correct value as per your country. For the USA it should be set to 115V and for the UK it should be set to 230V for other countries, you can check Wikipedia’s mains list.
  1. Try to print in a place where the temperature is neither too hot nor too cold. Additionally, make sure where you are printing the temperature is not fluctuating much.
  1. Always PID-tune your 3d printer whenever you are changing your filament, hardware, or any change that needs or does temperature manipulation.
  1. Do regular maintenance of your 3d printer, to clean out any dirt and find out broken wires and components. This tip will not only help you avoid any sort of error but also increase your printer’s life expectancy and improve print quality.
  1. Keep your firmware updated, by keeping your firmware updated you are reducing the chances of software-related errors and bugs.


In this article, I’ve given you the solution to fix the Ender 3 thermal runaway E1 error and additional tips to avoid it in the future in a very detailed yet concise manner.

I hope by this article I was able to help you troubleshoot the error and solve it without much headache and swiftly. If you still have any doubts or queries you can ask me in the comment box below.

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