I have just finished assembling my K8400 with two nozzles and one of their temperature sensors is reading 25°C, the other, 739°C. Obviously this is incorrect as the head is not glowing red. Naturally, I am receiving a ‘max temp’ error. I thought it may be because there was a poor connection and the high resistance was causing the temperature to be shown as too high, but upon unplugging the thermistor (infinite resistance) the temperature went to 0°C. This would imply that temperature increases as conductance increases, so I am not sure what might be causing the issue. Can anyone think of a cause for this problem, or a way to calibrate the sensors?
This sounds like a short on the thermistor.
You should follow the wires from the thermistor to the green connector block.
Make sure the wires for the thermistor are plugged in to the middle connectors.
If they are plugged in the proper place look for break in the insulation of the wire.
This is the case for the working thermistor, but the one in question has a resistance of about 18Ω. I measured this by disconnecting the thermistor and measuring the resistance between the two ends of the wire.
Turns out this is the resistance of the heater, which leads me to believe I had the contacts in wrong.