<p>It sounds like your Z limit switch is stuck.
The firmware will prevent the motor going further down past the limit to prevent damage.   Be careful going up because if the firmware doesn't know where the bottom is, it doesn't know where the top is.</p>

<p>I checked my printer (an i3 clone) and the limit switches are wired as NC (normally closed).  That means that the circuit opens when the switch is activated.  So, if the wire (or switch) is broken, or if it is unplugged, it will behave as if the switch is activated (the behavior you are seeing).  </p>

<p>An easy test would be to switch the x-limit and z-limit cables at the controller board.  If the problem moves to the x-axis, you have found your problem.  BE CAREFUL not to run the motor into the end stop and damage something since there is no limit switch to protect it.</p>

CC BY-SA 3.0
2017-05-17T23:56:24.883Z
2017-05-18T04:50:13.340Z
2017-05-18T04:50:13.340Z
markshancock
<p>If I send it commands to go up, the steppers rotate things up. If I tell the Z-axis to go down, nothing happens. I inverted the Z-axis in the firmware (by setting the value to true instead of false), and it did the same thing, but the other way around - it would only go down.</p>

CC BY-SA 3.0
2017-06-12T02:53:15.257Z
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Greenonline
<prusa-i3><marlin><electronics><z-axis><firmware>
My Prusa i3's Z-axis will only go up
D. Scott Boggs
# My Prusa i3's Z-axis will only go up

(Asked by: username_0 on 2017-05-17)

If I send it commands to go up, the steppers rotate things up. If I tell the Z-axis to go down, nothing happens. I inverted the Z-axis in the firmware (by setting the value to true instead of false), and it did the same thing, but the other way around - it would only go down.

**Tags:** prusa-i3, marlin, electronics, z-axis, firmware
> **Comments:**
> **username_1**: If the solution provided fixed your problem, then please mark the answer as accepted, otherwise it will remain in the [Unanswered Question](https://3dprinting.stackexchange.com/unanswered) list and as we are a beta site, in it important to keep this list as small as possible. If it did not then, please, provide more information. Thank you.  

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## 1 answers

### Answer by username_2 on 2017-05-17. Score: 3

It sounds like your Z limit switch is stuck.
The firmware will prevent the motor going further down past the limit to prevent damage. Be careful going up because if the firmware doesn't know where the bottom is, it doesn't know where the top is.

I checked my printer (an i3 clone) and the limit switches are wired as NC (normally closed). That means that the circuit opens when the switch is activated. So, if the wire (or switch) is broken, or if it is unplugged, it will behave as if the switch is activated (the behavior you are seeing).

An easy test would be to switch the x-limit and z-limit cables at the controller board. If the problem moves to the x-axis, you have found your problem. BE CAREFUL not to run the motor into the end stop and damage something since there is no limit switch to protect it.


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