Z-Axis Won't move down

Monoprice MakerSelect Plus
5.1 control board
3.1 BL Touch (Authentic)
ADVi3++ version 4.0.6 for 5.1 board with BLTouch 3
LCD firmware also 4.0.6

I can move my Z-Axis up and then down. However I cannot get it to move down to Z-Home. If I reboot the printer it resets the minimum height of the Z-Axis to the position at power off. If I turn off and manually move the Z-Axis down by turning the Z-rods that is the new home. I feel like I’ve jumped a step in configuration and I’m just not seeing it in the LCD panel.

Background: I’ve verified that my wiring is connected correctly, my soldering job is superb for the BL Touch. And yes I moved the jumper from the 24v position to the 3.3v position. BL Touch responds to LCD interface buttons. This does not appear to be a problem related to BL Touch installation. I have tried the 4.0.6 firmware for 5.1 board without BL Touch.

Where do you see you have to move jumpers? What are you talking about?

It’s technically a surface mount 0 ohm resistor. In the default position, power to the bl touch would be 24v and would fry it. Moved to the other position, it outputs 3.3v. I only mention what I did with the BL Touch install because I did it at the same time as the firmware flash. FHGYJ3GJDF2EBMP.LARGE

That’s wrong, at least if you have followed my instructions. I assume you have followed instructions from someone else.

In your diagram you have pin 2 on the z-probe to the white BL Touch cable. As I have done it I am using Pin 1 to the white cable. Moving the resistor to the secondary position causes pin 1 to output 3.3v. I have done this because pin 2 on the z-probe has a shoddy looking pad and didn’t want to try soldering to it. Aside from this I have followed your instructions and this is where I deviated. I don’t think this should account for the problem I’m having with the z-axis. Even with bl touch disconnected I continue to have the same issue.

For the sake of eliminating this deviation as a potential issue I am actively moving the jumper/resistor back to its original home.

All this was really not obvious in your first message.

What does that mean exactly? I do not see what you are doing.

This looks normal. When powering up, the firmware has no way to know where the head is.

I appreciate your help here. If I press Z-Home, the Z Axis remains in place unless I have previously told it to move up. It does not move down to the Z-axis stop. I’ve redone my wiring and moved the resistor back to its original home. The problem persists. When I attempt to use the Z-Height function in control, the printer homes X and Y, then moves to the center. Z-Axis goes up about a centimeter but does not go down. The BL Touch sensor extends the probe and pulls it back in.

But there is no Z-axis stop when using a BLTouch.

Here is a video showing the behaviour when I press press self test on BL Touch, then when I use controls, I press X home first, then Y home then when I press Z-Home.

Another video showing what happens when go to Controls > Leveling > Z-height

Looks like your BLTouch is not wired correctly but you have not answer to my question.

I’ve verified that it is wired up exactly as the instructions found here show. https://community.advi3pp.com/t/add-a-bltouch-sensor/21

I’ll have to take the printer apart again if you want a picture. But I’d rather avoid that. Even if wired incorrectly would it still not move down and end up crashing into the bed instead of sitting there motionless?

Your BLTouch turns immediately red, so it looks like it “detects” the bed immediately. Could also be the Z end stop (as you mentioned it) that causes problems. It must be disconnected.

And a lot (like really a lot) of people had problems with their wires. The Dupont connectors of the BLTouch are not the best way to ensure a proper wiring. They often make bad contact and when the head moves, it triggers the BLTouch.

Thanks for the suggestions. I’ve got a bin of connectors including the dupont. I went ahead and disassembled and check my wiring again and it looks good. I’ll give the wiring harness a swap and go from there. I appreciate you taking your time to give me a hand.

Thanks again for the help. It was the connector on the bl touch.

Which connector on the bl touch? I am having the exact same issue.

I am also having this issue. I was on an older version of the firmware, and then updated to the newest one. Before the Bltouch was working fine, now it wont move the z-axis down, and things z height of 0 is wherever I turn my printer off.