z axis homing problem

[jmontalvon]

Hello, my makergear m2 had a rambo 1.1 card that was malfuntioning so I bought a new rambo v1.3 and installed it. Everything is working fine but when I home z axis, it goes up until the limit switch but then it goes down like 15cm, stops, and then goes up again and stops 8cm from the nozzle. This happens in repetier and pronterface. The x and y axis have no problem homing, only the z has this problem. What could be wrong?

[sthone]

This behavior is usually from the bed hitting the nozzle before the z-stop bolt hits the limit switch?

Try this.... when the bed is homing toward the top manually press the limit switch by hand (before the bed gets to the top) and see if the bed stops as soon as you hit the switch.

If it does this means its working correctly and you just need to adjust your z-height so the z-stop bolt hits the switch before the nozzle.

If the bed still drops and the raises again after you hit the switch by hand you may have some other problem.

[ksevcik]

I'm betting you have the Z-axis limit switch plugged in backwards. Double check that the wire colors match what's silk screened on the board. A limit switch plugged in backwards ends up shorting 5V to ground and instantly killing most of the stuff on the board or completely rebooting the board.