How to: Ender 3 BLTOUCH with SD card support and no wires cut

The definitive guide for fitting a BLtouch to an Ender 3! Full SD card support and no wires cut in this easy to follow step by step guide.

ABL or auto bed levelling is a must for many Ender 3 owners because their beds have arrived warped. ABL will probe the print surface before each print and build a virtual mesh which alters the early layers to match the contours of the bed. The result should be a much better first layer and hopefully a better and more reliable print.

This is part 2 of a head to head ABL shootout, part 1 previously featuring the EZABL. The BLtouch emulates a folding servo and microswitch and is popular because it works on any build surface without recalibration. Other guides ask you to remove SD card support to make Marlin fit on the 1284P microcontroller, but some after worthwhile time spent in the firmware I found a way to have everything except the boot screen enabled.

This video assumes you have flashed a bootloader with my previous guide:

If you are getting this kit, make sure you buy directly from ANTclabs, not another vendor who is trying to rip them off.

Purchase the Ender 3 from these links:
Ender 3 Pro Banggood ($30 off with coupon 1d1c08):
Ender 3 Banggood (US warehouse, Coupon: f2bf59):
Ender 3 Pro Amazon:
Ender 3 Amazon:
Ender 3X (glass bed version):

BLtouch from ANTclabs on Amazon, adding 1m extension cable is recommended:
Pin 27 board (Aus eBay):
Pin 27 board (US – as part of the TH3D filament runout sensor):
Pin 27 board (eBay UK/Europe):
Pin 27 board (eBay US/Canada):
Pin 27 board (eBay UK shipping worldwide):

TH3D Unified firmware:
A guide I found handy for resources when starting my research:
Alternate guide without using pin27 adaptor:
Petsfang v2 fan duct:

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47 thoughts on “How to: Ender 3 BLTOUCH with SD card support and no wires cut

  1. UPDATE This guide is slightly out of date. It will still work well on the version I used here: U1.R1.10. There was a version of the firmware from TH3D after that had a bug that prevented this guide from working. This was fixed from U1.R2.1c. I have an updated guide using vanilla Marlin 1.1.9 with an option to spend a dollar to buy the files already configured:

  2. Just fried the main board on my Ender 3 following this guide 🙂 Hopefully its only the main board that's fried. I think the problem was switching the wires on the Pin 27 Board plug, it seems not all boards require this.

  3. Hello, I followed this tutorial using the TH3D Firmware U1.R2.7, had just a few differences, only 2 "BLTOUCH" search/replace and best of all, now there is no need to disable the boot screen anymore, it compiles to 98% of memory use at first attempt! Also, fortunately, my Pin 27 out must be ok because I did the swap like your instructions and everything is working fine. Autolevel is a MUST!!! Thanks!!!

  4. I just installed my BLTouch following your instructions. Many thanks! I have a couple of things to note for anyone doing this after 1/28/19. First, the latest version of Th3D doesn't need anything removed from it to compile down to the requisite size. I didn't have to edit out the boot screen, as you suggested and still had a compiled sketch that used 98% of the board memory. The second is a quirk that I discovered, and hope that it's helpful to others. I first tried to flash the firmware from a Mac using the latest version of MacOS (Mojave), and ran into all kinds of communication errors with the board in my printer. I first thought this was because I'd done something wrong in my wiring, but I could find no errors there. The easy fix to the problem was to use a Windows computer to flash the firmware. When I did this, everything worked just fine. Thanks again for this guide. I've learned much from it that I hope will make my Ender 3 prints even better in the future.

  5. Re: 3:24 "A couple METERS before the nozzle". Obviously you mean millimeters but I still have a question – if I unplug the servo so the probe is free to drop, should the magnet grab the probe before the nozzle hits?

  6. I followed all of your guides for this, I even flash the Unified Firmware when I had Marlin and for some reason the bed leveling isn't activating when i print. I am using Octoprint and Cura on my computer and uploading the gcode to Octoprint. I have tried it with the custom gcode in Cura, custom gcode in Octoprint and I cannot get it to actually work during a print. Please help as I cannot figure out what is going on and I have literally spent 8 hours trying to figure out what is going on and nothing.

  7. why splicing the rippon caple? And this adapter? – it´s pretty expansive. Just use a few jumperwires. Inexpansive, no sodering and reversible! 30 jumperwires – 0,7€. incl. Shipping from China 😛

  8. Hi Michael, I have a genuine BL Touch on an Ender 3 installed as per your instructions and it has been working really well until now. What is happening is that after the 9 probes the "leveling map" is being lost, especially on the left side of the bed. Unfortunately there have been a couple of times when the plastic probe has hit the bed clip on the left side, could this be the issue or is it something to do with the script? This is the starting script I am using that has been working well until now. At the moment my solution is to manually level the bed on the fly but thats not a proper fix.

    G28 ; home all axes
    G29 E; probe
    G92 E0.0 ; reset extrusion distance
    G1 X0 Y0 Z10 F6000
    G1 Z0.1
    G1 X6.0 E9.0 F1000.0
    G1 X5 Y30 Z0.2 F3000 ; get ready to prime
    G1 X100 E12.5 F1000 ; prime nozzle
    G92 E0.0
    Any idea what is going on would be much appreciated.

  9. After doing this, when trying to print, my SD card menu is EXTREMELY slow and lagging. Is there anything I could do to fix this? Printer runs perfectly if you can get the print started.

  10. No need to use a pin27 board and still no need to cut the buzzer wire. Just use 9 male/female dupont wires to extend all wires from ribbon cable to board connector except for the wire connecting to pin 27.

  11. Hi, is it possible to edit the firmware code to support the bltouch without arduino? (my printer already has th3d software, but i dont have the arduino) ?

  12. HI, I just got my first printer (ender 3 pro) and my bed is not totally flat, the middle is at a lower point than the edges. Would this modification help with it or should I get a new bed anyway ?

  13. Followed parts of your guide to get my BLTouch set up with the latest TH3D on my Ender 3 and it helped a ton, thanks!

    Side note: I made all the changes in this video to the latest TH3D (U1.R2.7) and still had 2% space left without having to disable anything. This means you can likely now have support for both ABL and a filament run-out sensor with only having to disable the boot screen. 🙂

  14. I just did this firmware update with the newest th3d version. After flashing my printer, it makes a constant loud beep sound from behind the screen, what could it be? Thanks

  15. I did this with the newer version of this firmware and there were only 4 changes in the configuration_backend. When it finishes probing it shuts off both my bed heater and my extruder heater then starts printing 🙁 Please any help would be appreciated.

  16. Got mine up and running with this guide. My firmware was a little different but I figured it out. Thanks. My 27 pin was in the proper configuration so no swapping wires. I have a controls and automation background so no problem "but" some people may have a bit trouble with this guide.

  17. Thanks for the great videos and keep 'em coming! One suggestion, though – when it comes to rewiring / re-pinning, would you please take a few extra minutes to dive into WHY you need to rewire something? I should have taken a closer look at my own rig before blindly following along, but I didn't… As previously commented, not all Pin 27 boards require swapping the 5V and GND wires (mine came from Amazon earlier this week). When I booted up after installing the mod, the fan started spinning and the LCD flashed intermittently, but nothing else happened. I pulled everything apart and sure enough, my Pin 27 was pinned to match the BLTouch connector! I swapped the red and brown wires back and was able to boot, flash, and test my BLTouch. Others, it seems, weren't so lucky!

    ALSO: A few days ago, Vampyrex13 posted a comment on thingiverse that very nicely sums up the firmware changes needed to make BLTouch work in TH3D R2.7 – Hope this helps others as much as it helped me:

  18. So after watching this video several times, the one thing that is completely missing from you instruction guide is tell people that the z switch that came with the original ender 3 will no longer be able be used.

  19. Hi Michael. Thanks so much for your great, well explained videos. I am new to 3D printing and have just bought the ENDER 3. I've followed your video regarding adding the bootloader which worked fine. The hardware side of the BLtouch is complete but using the latest download of TH3DUF_R2 Arduino 1.8.7 the sketch is a little different from the video. I've tried the best I can to follow your video but when I try to upload the sketch I get the following error:-
    In file included from sketchMarlinConfig.h:42:0,

    from sketchprintcounter.cpp:23:

    SanityCheck.h:830:8: error: #error "SERVO0_PIN must be defined for your servo or BLTOUCH probe."

    #error "SERVO0_PIN must be defined for your servo or BLTOUCH probe."
    I did change the line 165 to:- #define SERVO0_PIN27
    Where am I going wrong? Thanks Michael

  20. Has anyone had the situation where the extruder moves too far to the right and the fan hits the bolt heads ? I've tried changing the bed size with no success . Is it position to change the bed level position

  21. Something to consider is running positive and ground to the 6 pin area that you use to install your bootloader. Reason is i ran a bltouch through the 27pin adapter and yesterday my display got fried. Was it the bltouch or a bad screen? I really dont know. But i do know i wired my first ender 3 through the 6 pin setup 6 with signal only going to pin27 months ago never an issue. Wired in a bltouch to 27pin adapter all 3 wires and within 3 days my display goes bad. Not saying its a bad wiring idea because i always leave coincidence completely open when it comes to printers. But it may be worth checking into to see if others have had the same issue and if the alternate wiring is or isnt a better option. But thought this would be a good video for teaching tech to show multiple wiring possibilities since he does such a great job on ender 3 videos

  22. Sad that the Ender3 won't support both the runout sensor & BLTouch. I guess if I had to pick it would be….. BLT.
    Edit: Thanks, found the video, but didn't remember to edit my comment. There's also a way to do runout via the Pi & an Octoprint plugin.

  23. Need HELP….I recently install the BLT on my Ender 3 and followed your guide and it seemed to go great. Turn is on and it does it's self test, it responds to the commands in the firmware(THD 2.4) but when I try to home it , it drops the probe for Z axis and lowers but never stops, crashing into the bed. If I wanted to test the module manually, what kind of signal should I get out of it? I used the adapter board so there was no splicing.

  24. followed this guide using newest TH3D. I think I have it configured properly but am getting strange results. When I power on I get the self test up and down on the sensor. When I do the bltouch menu item test the pin just moves up and down never stopping. When I run the M48 test it initiates and even when the pin hits the bed it doesnt stop and will run the tip into the bed. (I power it off). I have run it again with triggering the pin early by manually pushing it up but it still runs down. Looks like it isnt zstopping at all. Any suggestions?

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