Fixing Connection Problems on a Duet WiFi: 6 Troubleshooting Steps

How to fix connection problems on a Duet Wifi.
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The Duet Wifi is a control board from Duet3D for 3D printers, laser engravers, and home CNC machines. I have been using it for my new 3D printer and have been happy with its features and performance so far.

Unfortunately, I ran into an issue where I suddenly could not connect to the board over Wifi anymore. After troubleshooting the connection problems, it turned out that the ESP-12S wireless module on the Duet had broken.

I did not want to pay another ~$200 for a replacement control board (especially knowing that it can just break like that), so I was a bit desperate to find a solution. Luckily it was possible to desolder and replace the broken ESP-12S module on the circuit board. With a couple of soldering tools and a bit of patience, this solved the problem.

In this article I will guide you through the steps of replacing the Wifi module. You can follow them to repair a defective ESP-12S or ESP-07S on a Duet 2 Wifi, but also to replace different ESP8266-based Wifi modules on other circuit boards.

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The newest versions (v1.05+) of the Duet 2 Wifi come with a different Wi-Fi module (Espressif ESP-WROOM-02D/U) that is more reliable. While in this article I replace a ESP-12S module on a v1.04 board, you can still use the same steps to replace an ESP-WROOM-02D/U, if necessary.

An ESP-12s Wifi module placed on a neutral background.

Troubleshooting the Duet WiFi Connection and Diagnosing the Problem

Replacing the ESP-12S module was not the first thing I tried to fix the wireless connection on the Duet 2 Wifi. I went through several other troubleshooting steps that I hoped would solve the problem. None of them did, but I will still go over them in case they are of use to you.

For context: The wireless connection on my Duet stopped working suddenly. One moment I was working on the 3D printer and everything was fine. Then I did some work on the printer that involved moving the extruder carriage by hand (more on that later). After that, the wireless connection disappeared.

These were the troubleshooting steps I took:

Resetting the Duet

Resetting the Duet with the onboard reset button was the first thing I tried. Needless to say, I still could not connect over Wifi after the board had booted up again.

Checking Whether the Duet is Connected to the Network

Maybe the problem was not with the Duet itself, but with something else along the connection path. Logging into the admin panel of the router showed that both the router and the network were fully operational, however.

What the router also told me was that the Duet was not connected to the local network at all. A good indicator that the problem was with the Duet itself.

Restarting the Wireless Module

Something else I did was trying to restart the ESP-12S Wifi module by sending M552 commands (M552 S-1 followed by M552 S0 and then M552) in the YAT terminal. This gave me a persistent “WiFi module is being started” response. No matter how long I waited, the module never finished starting.

A screenshot of a YAT terminal window with in it the response of an M552 command that was sent to a Duet 2 Wifi controller board.

Requesting the diagnostic information with an M122 command also gave a permanent “Network state is starting” message. Not a good sign.

A screenshot of a YAT terminal window with the status report of a M122 gcode command, highlighted is a

Creating a New Config File

At this point, I was pretty sure that there was some kind of hardware problem with the ESP-12S. But there were still a couple of things I could try.

The first thing was to generate a new config.g file. A long shot, but maybe something got corrupted in the old one. Honestly, I was grasping at straws a bit at this point.

I generated a new config file using the RepRapFirmware configuration tool and replaced the old one on the SD card, but once again without success.

Updating the Firmware

The next logical step was to update the firmware. Once again, maybe the old firmware got corrupted somehow. Worth a shot I guess.

The Duet Wifi was running on the 3.1.1 firmware release, which was already a recent version. But a 3.2 version got released a few days back, so I installed that version to see if it would fix the problem.

It did not fix the problem.

I also tried updating the firmware of the ESP-12S itself, but I could not get that to work. This made sense if the module was in fact broken.


After trying all these solutions, it was clear to me that only the ESP-12S/ESP8266 module was defective. During troubleshooting, everything else on the board worked normally when I sent commands in the YAT terminal.

There are several posts on the Duet3D forums that suggest having the Duet replaced under warranty in this situation. For me this was no option, as the warranty had already expired.

Replacing the ESP-12S was something I could do, so that’s what I decided to attempt as a last resort. I was pretty confident that this would work. Even if it didn’t, spending $5 on a replacement Wifi module was not a big deal compared to spending $200 on a whole new Duet.

My best guess as to why the ESP-12S broke is that when I moved the extruder carriage by hand, the stepper motors generated back EMF (the voltage generated when a motor acts as a generator) that damaged the Wifi module. In the future, I will either use the stepper motors to move the carriage or disconnect the stepper wiring before moving things by hand.

But for now, let’s take a look at how you can replace a defective ESP8266 module!

How to Replace a Broken ESP8266 Module

You can use these steps to replace any ESP8266-based module that is soldered directly to a circuit board. Common examples are the ESP-12S, ESP-07S and ESP-13. They are all fairly similar and are typically attached to the PCB in the same way (soldered).

If you use an ESP8266 module with pin headers you can obviously just remove it from its socket and swap it out with a replacement.

What You’ll Need

Tool icon Tools
Weller SP40NKUS 40-Watts Soldering Iron Kit Red/Black, 5 piece
Hot Air Rework Station, 858D SMD Desoldering-Gun (212-932°F) Kit with °F...
SE 7-Piece Vacuum Pen Set with Interchangeable Tips and Cups - EL-VP6
Tweezers are also okay, but they are more fiddly to use for this.
KOTTO Solder Smoke Absorber Remover Fume Extractor Smoke Prevention...
Strongly recommended for any (de)soldering
Part icon Parts
If you have a Duet Wifi with an ESP-12S, you can swap it out with an ESP-07S and vice versa. The ESP-07S has an external antenna that provides better Wi-Fi signal.
MG Chemicals - 8341-10ML 8341 No Clean Flux Paste, 10 milliliters Pneumatic...
NTE Electronics SW02-10 No-Clean Solder Wick, 4 Blue, 098' Width, 10'...
AUSTOR 60-40 Tin Lead Rosin Core Solder Wire for Electrical Soldering...


The first step in replacing the wireless module is to remove it from the circuit board. This might seem like a daunting task if you have never desoldered before, but it is fairly straightforward and I will guide you through it.

Top view of a blue silicone soldering mat with a circuit board on top and a variety of soldering tools spread around it.
Prepare the work area by putting everything you need within reach. If you want to protect your work surface, you can use a silicone repair mat. This provides a heat resistant layer that helps protect the surface from any heat. If you have a sacrificial workbench, this is not really necessary.
A syringe with flux being used to apply flux onto a row of solder connections.
Apply flux to the solder joints of the ESP8266 module. The flux that I use came in a syringe, but it’s possible that yours comes with a brush or some other applicator. Whatever it is, use it to apply a decent amount of flux to the solder joints.
The front panel of a Quick 861DW hot air rework station with its settings visible on the LCD screen.
Configure the hot air rework station settings and turn the device on. On my Quick 861DW I set the temperature to 370°C (698°F), the airflow to high and used a medium sized nozzle.
Hot air from a nozzle melting flux on solder joints.
Start heating up the area with the rework station nozzle. You can see here that I used an angled nozzle. This makes it easier to direct the air onto the right spots.
A hot air rework station nozzle melting the solder on a defective ESP8266 wireless module.
Continue applying heat to the area. The flux melts quickly, but the solder takes a bit longer. Just keep applying heat to the pins. Try not to keep the nozzle in one place for too long. Instead, continuously move it around over the pins.
A hot air rework station nozzle blowing hot air on a PCB with a vacuum pickup tool being held on a broken ESP-12S module.
Once the solder joints have melted, remove the ESP module. You can use a vacuum picker tool or a pair of tweezers for this. Keep applying heat while removing the module from the board, we don’t want the solder to harden halfway through the process.
An ESP-12S module being lifted up with a vacuum pickup tool front of an out of focus circuit board.
The module should come off without too much effort. If you do find the removal taking effort, you need to continue applying heat until the solder has properly softened.
A black marker being used to mark a cross on the top metal cover of an ESP8266 module.
Mark the old ESP8266 module as defective. This makes sure that you don’t confuse it with a working module later on. Disposing of the module is not an option yet, as it is extremely hot at this point.

Cleaning the Solder Pads

Before soldering the new module to the board, we must first clean the solder pads. We want to create good connections and old flux and solder are not going to help with that.

Solder wick and a soldering iron being used to drag away leftover solder from a circuit board.
Use a piece of solder wick to remove any leftover solder from the pads. I find that the best way to use solder wick is to add flux to it and slowly drag it with the soldering iron on top over the pads. This will draw in any solder.
A cotton swab soaked in alcohol being used to remove flux residue from a PCB.
Once you have removed the solder, clean the pads with a cotton swab soaked in alcohol. This removes any leftover flux residue.
Close-up of very clean soldering pads on a circuit board.
The pads should now look something like this. It does not have to be perfect, but the cleaner, the better.

Soldering the New ESP8266 Module Onto the Circuit Board

A vacuum pickup tool being used to replace an ESP-12S Wifi module on a Duet 3D printer controller.
Put the wireless module in its designated place on the circuit board. You can use a vacuum pickup tool, tweezers, or just your fingers for this. It doesn’t really matter, as long as the module ends up aligned with the soldering pads.
Solder and an iron being used to form a soldering joint between an ESP-12S wireless module and a Duet 2 Wifi.
Solder one of the corner pins to its corresponding pad. If you are happy with how the module is aligned, continue to the next step. If not, melt the solder and realign the module.
A soldering iron melting solder to attach a wireless module to a PCB.
Now solder the opposite pin. By soldering these two pins first, we can be sure that the module stays properly aligned while we solder the remaining pins.
A soldering iron being used to solder the pins of an ESP8266-based wireless module onto a Duet 2 Wifi..
Solder the remaining pins.

Inspecting the Solder Joints

Close-up of the solder joints on a freshly replaced ESP-12S Wifi module on a PCB.
The end result should look something like this. All pins cleanly soldered to the pads on the circuit board.

If you have access to a microscope, you can use it to inspect the solder joints up close. But in this case you use any kind of magnification, or even do it by eye (if you have good eyes). The pins on the ESP modules are fairly large and are relatively easy to inspect compared to pins of typical SMD components.

An orange arrow pointing to a faulty solder joint on an ESP-12S Wifi module.
After I was done soldering the ESP-12S, I used my microscope to identify one pin that was not soldered properly to the pad.
A screenshot from a digital microscope screen that shows eight soldered pins of an ESP8266 wireless module.
A quick resolder of the joint and I was ready to continue.

Updating the WiFi Module Firmware & Testing

There are still a couple of things that need to be done after soldering the new module in place. The first is to update the firmware of the Wifi module. On the Duet this can be done as follows:

  1. Download the latest DuetWifiServer.bin from the Duet3D firmware page.
  2. Place the DuetWifiServer.bin in the /sys folder of the Duet SD card.
  3. Send an M997 S1 command to the Duet using the YAT terminal.
A YAT terminal window that shows new firmware being uploaded to an ESP8266 Wifi module with a M997 S1 Gcode command.
If everything is right, you should see something like this.
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More detailed instructions on updating the firmware can be found on the Duet3D Wiki.
Screenshot of YAT terminal window. Highlighted are
Starting the Wireless module by sending M552 S0 and following up with an M122 should now show a working Wifi module.

After that, it is just a matter of connecting the Duet to your Wifi network as usual.

A powered on Duet 2 Wifi 1.04 controller board with plugged in USB cable.


If you can’t connect to your Duet Wifi anymore, then there are a couple things you can try to fix the connection problems. If none of these work, it is possible that the ESP-12S or ESP-07S wireless module is broken.

No worries, there is no need to buy a brand new Duet 3D printer controller. With the right tools you can replace the module yourself and get your 3D printer or CNC up and running again.

It is important to not attempt this without access to a hot air rework station. With just a soldering iron it is practically impossible to keep all solder joints of the wireless module molten at the same time.

Author image
Tim is an expert in 3D printing, laser cutting, and 3D scanning with a background in mechanical engineering and product design. With decades of experience, he offers in-depth insights and practical solutions, contributing to his reputation as a trusted resource for DIY enthusiasts and professionals.

7 thoughts on “Fixing Connection Problems on a Duet WiFi: 6 Troubleshooting Steps”

  1. I would replace the onboard module with ESP8266 Esp-07 WIFI transceiver module, it has an external IPX antenna socket.

    1. Good question! In theory, it should be possible. In practice, it might be difficult to desolder the Ethernet module because of its large size. We don’t have any hands-on experience with the Ethernet version, so we can’t tell for sure.

  2. Thank you so much for this article! I have this 1.04 board when the WIFI LED went out and no WIFI is available anymore… So identical to your situation.
    But before I order a new ESP-12S module I was wondering if it possible to install the
    Espressif ESP-WROOM-02D/U instead?

    1. Yes I had the same question. I am going from ethernet to wifi conversion, I just wanna ditch the cable so I’m going with ESP-07S for now. But I will add a separate BL module
      for more options.

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