Z Axis Jammed

I had a bad thermister so I replaced it. Now the temperature works great, but the Z axis is stuck in the highest position and even if I manually screw it down, all functions send it right back up to the top of the printer. Does anyone have any suggestions?

did you have to unplug the Z axis cables? if so. is there any chance you reversed them both? ordinarily on home it is going to run down the leadscrews until it hits home. If it is running up, the motors are reversed, or something wierd is occuring.

The Mini homes to the top of its Z travel. You need to see if it is giving any errors in the console window for the printer control program(like Cura).

I initially did not unplug any Z-axis cables, but after the problem I tried to switch the cables around to see if it would help and there was no change. Regardless of the orientation of the cables it just goes up and stops at the top. The Cura window just reads that the Z-axis has reached its end at like 161. Not sure what could have cased this error. I also tried to update the firmware and no change. Really stumped.

I had a Mini at one time, but if the Z limit is at the top of the travel, is it being actuated? Its news to me, I did not think you could reverse the plugs going into any stepper motor. I-T-W also posted on here at one time about a short in the thermistor or wiring to ground causing weird things to happen.

they are keyed, but if you reverse the wire pairs, the motor will operate in reverse without issue. If the key notch is missing, it would be possible to plug them in wrong. It would be odd though for that to occur, but I figured it was worth mentioning since some part replacing occurred.

As I also recall the Mini has two Z motors, so he would need to reverse both and removing the wires (pins) from the keyed plug would be a tough job. But the I T W thing I do remember being posted, and its worth checking to see if the Z homing switch is being activated, at the correct point. Yes I have converted a milling machine to a modern stepper system control system and worked on a few others.

The cover that is removed to replace the thermisitor also has the heater. So if you had a short occur then you would blow the end stops. Does it preform the X home and the Y home using the control window home buttons.

Yes the X and Y Axes work fine in the control window of Cura. If I manually bring the z axis down and hit home it goes all the way back up to the top and will not come down. Is the heating element somehow connect to the Z axis? That would seem an odd pairing.

Also I was wrong about reversing the motor wires. I apparently was working with the limit switches which had no effect on the up or down direction of the motors.