BLTouch 3.1 on Ender 3 Pro 4.2.2 - Blinking Light Mid-Print

Hey everyone,

I’ve just got around to installing my BLTouch on an Ender 3 Pro (running the most current TH3D Unified Firmware). I’ve got it plugged in to the Z-axis stop, and can run the homing wizard just fine. Before starting a print, all signs pointed to it functioning properly.

The challenge I’ve got now, though, is the BLTouch pin will deploy at random intervals while printing and then throwing up an error code by way of a blinking red light. The way it deploys looks like the way it homes when you first turn it on - dropping twice to touch the bed and stowing afterwards. The print appears to be able to continue just fine - and I have since disconnected the BLTouch mid-print - but obviously I don’t want to have to do this each time I print something.

I’m mid-print right now, so I’ll be attempting to tighten the grub screw on the top when the print completes and testing them - I suspect the pin wasn’t being held tight enough, but I have no idea.

Has anyone else had this issue? What did you do to fix it? If you need more info about my setup, let me know!

Try printing one of the Ender 3 sample/test files that came with the printer. They are obviously sliced for the Ender 3’s default configuration and as such, will make no reference to the BLTouch. You are testing in this case, for a behaviour that is isolated to the BLTouch, and the associated control circuitry on the controller board. If you print a model where you know the slicer didn’t insert any BLTouch related commands, then nothing should happen.

If that prints OK, open the .gcode file that gave you problems and search for BLTouch related codes. M280 is the only one I’m aware of, but I don’t use a BLTouch so I have no first-hand experience.

If the test print did not print without the BLTouch being activated, or there are no BLTouch related G-Code commands in the problem file, I’d be suspicious of the firmware. Try reverting to an earlier version or googling “bug reports” for that brand of firmware to see if this has been reported by others.

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I haven’t tried printing the original models yet, but that’ll be the next thing I go for if my current change doesn’t work. The bug reports, though - that got me somewhere!

My extension cable had a 3-pin female Dupont connector that I plugged right in to the board’s JST connector, so I figured that could also have been a weak link since I was getting the “bad connection” error (blinking LED, 80% duty cycle). I swapped the Dupont over for a JST and got it plugged in and started printing a calibration cube. It seems to be holding up so far. I might also not have enough slack in the cable on the print-head end as well, now that I’m looking at it through that lens, so if it acts up tomorrow I’ll pull a bit more through and give it some extra space.

If it stops working with my sliced models, I’ll grab one of the ender 3 originals and try it with that.

Thanks for the quick and detailed response - it definitely got the gears turning (even if it took me somewhere else!)

An update for completion’s sake: it was a connection problem. Replacing the connector inside the control box with the proper one and pulling more slack through on the hot end side seemed to have cleared up whatever issues there were.

Thanks for updating us. I’ll keep cable slack in the back of my mind when people report BLTouch problems.