Why Is My BLTouch Not Deploying? (How to Fix It?)

We can all agree that correctly leveling the bed is paramount to the success of the printing process, as a bed that isn’t level can cause all sorts of problems ranging from inconsistent extrusion to physical damage to the build plate and the nozzle.

On the other hand, as getting consistent results through manual bed leveling can be challenging, an ABL sensor, such as the BLTouch for popular Creality printers like the Ender 3 (Pro/V2), Ender 5, and CR-10, is usually one of the first upgrades that enthusiasts get for their printers.

Today, our topic will be an issue that troubles many 3D printing enthusiasts who install a BLTouch auto bed leveling probe on their 3D printers, which is the pin of the BLTouch not deploying at all during the auto-homing process.

So, what can cause your BLTouch not to deploy?

Below are the most common culprits behind the issue of BLTouch not deploying as it should:

  • Stuck BLTouch Pin
  • Misconfigured Probe Z-Offset
  • Misconfigured Firmware
  • Incorrect Wiring
  • Defective BLTouch Probe

Next up, we will talk about the issue of the BLTouch probe not deploying in more detail to find out the possible culprits, discuss what to do to fix the problem, and finally, take a quick look at signs that indicates your BLTouch is working correctly.

Why Is My BLTouch Not Deploying?

Seeing that your BLTouch is failing to deploy during the auto homing process can be pretty upsetting as it’s a surefire sign that the probe isn’t working as it should.

Stuck BLTouch Pin

The most apparent factor that can prevent your BLTouch from deploying is a stuck pin, where the probe isn’t physically able to push the pin out of its body towards the build surface.

As the pin of the BLTouch probe is a small object made out of plastic, and as the motor that pushes this pin isn’t very strong, it’s pretty likely for the pin to be stuck due to numerous reasons, such as dust and dirt blocking its movement or it being slightly bent to name a few.

Since the BLTouch isn’t the most durable device by any means, we highly recommend keeping the possibility of a stuck pin in mind before moving on to different culprits.

Misconfigured Probe Z-Offset

A misconfigured probe Z-offset value can easily be the reason behind your BLTouch not deploying.

In a nutshell, if you incorrectly configure the probe Z-offset value, the BLTouch will either be too close to the build plate or too far away from it during the automatic bed leveling process.

If the BLTouch is too close to the bed, the pin might not have enough space to deploy correctly, and on the other hand, if the BLTouch is too far away from the bed, the pin won’t touch the build plate, causing the process to fail.

Since using a probe Z offset value that brings the printhead way too close to the bed can damage the BLTouch, the printhead, and the bed by causing the nozzle to crash into the build plate, it’s vital to be careful with this one.

Misconfigured Firmware

Another problem that can cause your BLTouch not to deploy as intended is misconfigured firmware.

As with anything else on the 3D printer, the firmware is in charge of controlling the auto bed leveling sensor, meaning that the firmware needs to support the BLTouch for the BLTouch to deploy.

While Marlin Firmware contains the necessary code for the BLTouch to operate, the BLTouch functionality is disabled by default, meaning that the BLTouch won’t work with the default version of Marlin.

Considering that not every 3D printer that runs Marlin has a BLTouch attached to it, it makes sense that the default version of Marlin ships with the BLTouch functionality deactivated.

Incorrect Wiring 

Problems with wiring mean that the BLTouch cannot operate correctly, meaning that the pin most likely won’t deploy.

For the BLTouch to work correctly, all of the wires should be connected to the appropriate pins, and they shouldn’t have any damage that prevents them from transmitting.

As the wiring diagram can be technically complex for someone who isn’t familiar with electronics, incorrect wiring is one of the most common issues that prevent the BLTouch from deploying.

Defective BLTouch Probe

If everything else seems to be in order, a defective BLTouch probe could be the cause behind the issues you’re facing.

Defective BLTouch probes are a widespread problem that gets talked about often in the community, especially due to the existence of cheaply made clones that look like the real BLTouch.

In this scenario, the unfortunate truth is that you will need to replace your BLTouch with a new one and ensure that the device you buy is authentic to avoid the issue of a defective probe as much as possible.

How to Fix BLTouch Not Deploying?

While the simplest way to fix the issue of BLTouch not deploying is to find the root cause first, sometimes it’s much more effortless and less time-consuming to go through the solutions for all possible causes.

Below, we have listed the fixes for every possible factor that can prevent your BLTouch from deploying, which you can either follow in order or pick the appropriate solution out of if you know the root cause:

  • Unscrew the BLTouch pin and ensure that it can move up and down freely without obstructions. As unscrewing the pin will allow you to pull it out of the probe, it’s also a good idea to clean the pin and its path to ensure no friction working against its movement.
  • Re-configure the probe Z-offset. We have a detailed guide on setting the probe Z offset with the M851 G-code that you can follow to conduct this process.
  • Re-configure the firmware and re-flash. We highly recommend referring to the Marlin firmware documentation on configuring Z probes for this fix, which will always contain the most updated information to enable BLTouch functionality in Marlin.
  • Re-do the wiring of your BLTouch. We recommend referring to the BLTouch wiring documentation for the best results possible, as the correct way to do the wiring varies among printers.

We highly recommend running the BLTouch self-test process after applying each of these solutions to find out whether the fix has worked or not.

How to Tell If BLTouch is Working Correctly?

While the BLTouch comes with colored LEDs that flash in different patterns to communicate the current situation, the process for understanding the meaning of these patterns isn’t too straightforward.

As long as the BLTouch completes the automatic bed leveling sequence initiated by the G29 G-code and the printing process starts after this sequence without any intervention, your BLTouch should be working correctly.

During the automatic bed leveling sequence, you can observe that the BLTouch moves towards multiple distinct points on the build plate and pushes the pin outside in a way where it touches the build plate to take the necessary readings for leveling the bed.

To get more information about the LED color codes of BLTouch, which provide more insight into the probe’s operating status, we highly recommend referring to the BLTouch manuals. While the terminology is slightly technical, it’s the best way to understand the signs that show whether your BLTouch is working correctly or not.

Wrapping Up

Even though BLTouch not deploying is a common issue that many 3D printing enthusiasts who install the probe to their printers for the first time face, the problem is solvable in most cases by taking the appropriate action.

To wrap up, we can say that a stuck pin, a misconfigured probe Z-offset, a misconfigured firmware, incorrect wiring, and a defective BLTouch probe are the most common reasons that can prevent your BLTouch from deploying.

Except for the cases where the unit is defective, the issue should be relatively straightforward to solve by quickly going through all of these factors and applying fixes to ones that require it.

Happy printing!