Z axis drive will only go down, not up

[Trehearne]

I have recently assembled my Geeetec i3 pro B and all is OK with the exception if the Z axis drive. Apparently it will only go down. I am unable to make it go up either on the control panel or through Repetier-Host. When it travels down and hits the end stop micro switch there is no slight bounce that occurs when the x and y axis hit the end stops, only a growl from the stepper motors. Any ideas please. Thanks, Ralph

[Gingko]

It might be the problem with the endstop of Z-axis.
You can send M119 to check it, follow steps from this post:
viewtopic.php?f=17&t=17037

[Gingko]

or have you checked the wiring of Z endstop?
It should be plugged in Z min.

[Pizara]

This is due a shortage of voltage on the 'z' driver on your motherboard. I had the same issue.

There is a little potmeter (philips screw) on the driver. You need to boost the voltage up to a least 0.8 or 1 volt.
You can easily measure this, just put your voltmeter between the GND and the potmeter on the driver.

Good luck!

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