Issues with the BLTouch

  • So I have an original BLTouch connected to my Wifi for some weeks now, the BLTouch is used as the Z-Endstop too.
    It is basically working, but a lot of times when Z homing in the beginning if a print job, the BLTouch pin is just not lowering, but instead the BLTouch goes into error condition and is blinking.
    I reset the BLTouch then and try again, but same thing, it goes into error conditon. If I move the pin by hand a couple of times up and down and then give the M401 / M402 command manually a couple of times, then the Z Homing is working. That is very annoying, so maybe somebody knows a solution too this?

    I have the latest BLTouch with serial number on it, so no resistor needed and I cut the bridge on the logic board of the BLTouch like stated in the Antlabs manual. The BLTouch is connected as Heater 3 to the Duet
    My config.g for the BLTouch is this:

    M307 H3 A-1 C-1 D-1 ; Heater 3 reserved for BLTouch
    ;Lines for BLTouch
    M558 P5 X0 Y0 Z1 H5 F120 T2000
    G31 X40 Y5 Z0.68 P25

    and my homez.g is this:

    G1 Z5 F200
    G1 X141 Y100 F2000
    M401 ;Deploy probe
    G30 ;Find Z
    M402 ;Retract probe
    G1 Z5 F200

    I am using M280 P3 S10 I1 for deployprobe.g and M280 P3 S90 I1 for retractprobe.g. I think i did all things according to the Wiki connecting a Z-probe to the Duet. Still have this annoying problem.

    Thanks for your time…

  • administrators

    What does the bltouch manual say are the causes of it going into an error condition?

  • I have a BLTouch that exhibits the exact same behaviour. I have to pull the pin out at least once before it will start to act correctly.

    Never found a solution.

  • Hey guys.

    Just an idea, but have you taken the grub screw out the back and checked/cleaned the pin?
    I didn't have this issue with mine, but had to check and reset the bltouch this way as I was convinced it wasn't retracting quite far enough to stay retracted at times.
    So far so good since I took it apart, but mine is a clone so probably not made the best.

    It could be there is some debris in there maybe stopping the pin working smoothly, or the heat shrinked section at the back is catching. As it relies on a magnetic field to move the touch pin in and out, any increased friction won't help it work smoothly. But also from what I'd read, the rear portion needs to be within the right band for the magnetic field to work properly at extending and retracting the pin.


  • David, the BLTouch "Manual" is a 2 page PDF that does not say anything about any error conditions. is pretty much it.

    The BLTouch just starts to blink, if something is wrong, but does not say why.

  • And coolice, my BLTouch is brand new, I inspected it, there is no dirt or whatsoever in it, it CAN move freely, just doesnt.

  • There is an adjustment, that's supposed to factory set at 0.3 mm, but can still be user changed. Its the height of the grub screw. Changing it will vary the amount of magnetic force applied to the core.

    Dimension should be at 0.3mm. It will be my next action to fix it, just have not had time.

  • Yup, I have the exact same problem. I move the pin manually up and down a few times and it's fixed… until it happens again. I will have to see about the grub screw.

  • @Biggsis:

    And coolice, my BLTouch is brand new, I inspected it, there is no dirt or whatsoever in it, it CAN move freely, just doesnt.

    Ah cool. Well as I mentioned and with the link posted above, it might be worth checking the grub screw height/set point.
    I'm sure mine wasn't set correctly so the magnetic field wasn't driving the pin correctly.


  • I've had the occasional problem with this also, but for me, I put them mostly on the duet misbehaving, or me,as it only seemed to happen when I turned on the machine, and a clean power cycle cleaned it up. I really haven't had an issue since I finished up my wiring, and I've never seen it fault through multiple prints.


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