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I have a new H2 with the HE280. I went to start the first PID tune of the hotend during initial calibration and noticed the temp never went up. I checked the heater block and noticed it was very hot but the temp reported on the LCD is still about 25°C. If I set a new temperature via the LCD, the target temp changes and the hotend still gets hot, but you wouldn't know it per the LCD - it never changes from ambient. The fan also runs non-stop at full speed from the moment I turn it on, even if it's cool. If I unplug the green and white wires from the mini RAMBo, the temp still shows up on the display at around 25°C, and the fan finally slows to a much lower speed. I'm at a loss as to how to troubleshoot next since I can't seem to get the thermistor to even disconnect/go blank from ambient.

Any help would be greatly appreciated!

I would contact support on this one. When you unplugged the thermistor, it should've gone to "def" right away. Could you have accidentally plugged it into the bed thermistor connector by chance?

tnx.

g.