Prusa i3 Z motors & extruder thermistor issues

tl;dr:
Z motors beep instead of moving.
Thermistor resistance decreases when connected to RAMPS board.

Hey guys, I'm building a Prusa i3x that I got from DIY Tech Shop and I'm having issues with my Z motors. I'm using Marlin firmware, a RAMPS 1.4, an Arduino Mega, and Repetier-Host to control the printer. Using manual controls, when I try to move the Z motors they just make a beep/whirring noise (like they are trying to turn) and then stop. The X and Y motors work fine and when I plug the Z motors into the X or Y outputs on the RAMPS board, they work just fine. Also, when I try to move any of the motors 10mm or 50mm, it makes that same beep noise and only moves about 1mm. Any ideas on what the issue might be?

Additionally, for some reason the extruder temp keeps reading high (110 C at room temp vs bed temp @ 26 C). The resistance of the thermistor is 100kΩ when measured without any power, but when the Arduino is connected via usb the resistance drops to about 4kΩ and stays low for a few minutes after the thermistor is disconnected - voltage while connected is just below 1.7V. The thermistor wires are not touching the extruder block at all, are separated, wrapped with heatshrink tubing, and soldered to the wire connected to the RAMPS board. I tried removing it from the extruder, resoldering, and reattaching it to the extruder but still have the same issue. Any thoughts on why this might happen?

Thanks!

Quote
deyjoo
tl;dr:
Z motors beep instead of moving.
Thermistor resistance decreases when connected to RAMPS board.

Hey guys, I'm building a Prusa i3x that I got from DIY Tech Shop and I'm having issues with my Z motors. I'm using Marlin firmware, a RAMPS 1.4, an Arduino Mega, and Repetier-Host to control the printer. Using manual controls, when I try to move the Z motors they just make a beep/whirring noise (like they are trying to turn) and then stop. The X and Y motors work fine and when I plug the Z motors into the X or Y outputs on the RAMPS board, they work just fine. Also, when I try to move any of the motors 10mm or 50mm, it makes that same beep noise and only moves about 1mm. Any ideas on what the issue might be?

Additionally, for some reason the extruder temp keeps reading high (110 C at room temp vs bed temp @ 26 C). The resistance of the thermistor is 100kΩ when measured without any power, but when the Arduino is connected via usb the resistance drops to about 4kΩ and stays low for a few minutes after the thermistor is disconnected - voltage while connected is just below 1.7V. The thermistor wires are not touching the extruder block at all, are separated, wrapped with heatshrink tubing, and soldered to the wire connected to the RAMPS board. I tried removing it from the extruder, resoldering, and reattaching it to the extruder but still have the same issue. Any thoughts on why this might happen?

Thanks!

Turn acceleration down and check v-ref.

Did I read correctly that you soldered the wires to Ramps? That is a nono...but if you have the correct thermistor selected in firmware and have checked everything, Ramps or the Arduino is probably bad.