I may have the same problem. I sent this email to customer support and am waiting for a reply. Have you had any luck ?
Good Morning,
I hooked up the gShield to the Arduino Due and followed the setup information from this site:
https://github.com/synthetos/grblShield/wiki/Using-grblShield
I have 3 motors and all work on the X and Y controller ports and none work on the Z port. When I enter a command in Chillipeper like G0X1000 the motor turns for almost a second and stops for X and Y, but when I enter G0Z1000 the controller runs endlessly. I start the Z Motor Current pot all the way counter clockwise and slowly turn it clockwise and hear the fan on the power supply increase indicating its drawing more current. I have verified (several times) that the input from the power supply to the gShield is 24.0Volts etc.
Please advise how to determine if the Z port is bad on this board.
thank you,
Bryan Holocker
