Troubleshooting and Install of the BL Touch on the Ender 3 Max (or others!)

The BL Touch is a wonderful tool to enhance your 3D Printing setup. Like me, you were probably expecting a plug and play style installation. What reality ends up being is you’ll likely run into multiple issues. Thankfully, after spending 12+ hours troubleshooting, there are some things I hopefully can share for some of you who are still scratching their chin trying to get their BLT setup for the first time. 

At the writing of this guide, 2021, most people likely are new owners of 3D printers and will probably have a Ender 3 4.2.2 32 bit board , so this guide is tailored to that. 

I must give credit to this guide for helping me out, at least half way, and encourage you to use it as reference as well (if applicable). I’d like to echo this author and encourage you get at least the 1.5 meter extension cable, as the 1 meter wasn’t quite cutting it. 


Referencing the above guide, we see this diagram below for the wiring on a 4.2.2 board: 

For my scenario, I purchased the antclabs type extension cable (right).

While the wiring diagram is accurate, the pin connectors are just not quite the right fit. Although slightly smaller, they do slide in there, and do indeed make a connection, but are extremely prone to sliding out, especially the two slot connector. Even if they don’t slide out, they can still lose connection, even while physically still being in the slot. You wouldn’t believe how many time how confident some of my issues weren’t wiring, when they were just that. So keep an eye out for that.

On that note. If you received those cables, they are known as Dupont connectors, and what it’s connecting into is what’s known as a JST XH slot. Although similar, and they kinda fit, your best bet is to splice in the proper connector (JST XH), print out the connector ends if you can (I couldn’t with my nozzle size), or simply glue gun the connectors the lazy way, like I did. 


Below is another wiring guide for 4.2.X boards, use with caution and as a last resort. It should work in theory, as you’re just replacing the Z endstop connector with the BLT signal cable (2pin). Though, many people have these connectors occupied and glued in. 

Z-Axis Issues

If your BLT is lighting up, but refuses to go down in the Z-Axis, it could be that the two pin connector isn’t making contact on the board. 

Brown/Red/Yellow cable is three pinned, less prone to losing contact, and it’s the power to the BLT, it also controls the pin going up and down. The two pin black/white connector is responsible for controlling the Z axis. If you haven’t secured this pin with the proper connector or glue, consider troubleshooting it by holding the pin in gently while running a bed leveling test, moving it around or reseating it as necessary until the test can successfully move downward on the Z-axis. 

Firmware issues

When I attempted to follow the above Smith3D guide, the included pre-combiled .bin for the Ender 3 Max with BLT didn’t work for my printer. So I compiled my own using Marlin 2.0.8 and configured for the Ender 3 Max. Feel free to download it!


  • Many connectors sold on Amazon come with Dupont connectors, which connect to a JST XH on the 4.2.2 board. It does fit, but it easily can slide out of place. Even if it physically looks in the slot, it can lose connection due to the larger holes.
  • Consider splicing, printing out the right connector size, or glue gunning for the above issue.
  • If your Z-Axis won’t move down, it’s because your white/black connector is loose.
  • If you own a Ender 3 Max with BL Touch, included above is a 2.0.8 Marlin firmware (newest) that has all BL touch features enabled

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