HMS 0300-1E00-0001-0007: left nozzle temperature sensor open circuit
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HMS 0300-1E00-0001-0007 means the temperature sensor in the left nozzle reads as an open circuit. The printer cannot know how hot that nozzle is, so it refuses to heat it at all: a hotend without a working sensor is the one genuine fire risk on a 3D printer, and the firmware treats it that way.
Affected machines: H2 and X2D. These are dual-nozzle machines, so the fault is confined to one half. Single-material prints assigned to the right nozzle will still run, which buys you time to order the part rather than losing the machine entirely.
Where to buy
Connector first, then the sensor
An open circuit means the path is broken, and on a toolhead the most likely place for a break is a connector rather than the sensor element itself. The left hotend plug is disturbed every time anyone works on the toolhead, and a pin that has backed out of its housing produces exactly this reading.
Measure at the hotend rather than at the board, so you know which side of the connector the break is on. A healthy sensor reads around 100k ohm at room temperature. The left one should match the right one closely; if the left reads open and the right reads normally, you have both confirmed the fault and eliminated the board.
Left nozzle will not heat and the printer reports its temperature sensor as open circuit
Broken connection at the toolhead connector, occasionally a failed sensor inside the hotend
- Power off at the wall and let both hotends cool completely.
- Unplug the left hotend connector and inspect the pins in both halves under good light.
- Measure the sensor at the hotend side. Around 100k ohm cold is healthy; an open reading confirms the fault.
- Measure the right-hand sensor the same way as a reference, so you know what a healthy reading looks like on your machine.
- Reseat the connector firmly and measure again at the board end to isolate the cable.
- If the sensor at the hotend reads open, fit a replacement hotend assembly, because the sensor is not sold separately.
Do not try to force the left nozzle to heat by clearing the error. Without a sensor there is no feedback, and a heater with no feedback is the one failure on a printer that can start a fire rather than ruin a print.
The right-hand equivalents are right nozzle control abnormal and hotend temperature sensor fault. Our page on dual nozzle printers explains what the second tool is for, and the troubleshooting index covers the rest.
HMS 0300-1E00-0001-0007 FAQ
Can I keep printing on the right nozzle?
For single-material jobs assigned to the right tool, yes. Anything that switches nozzles will stop.
Can I buy just the sensor?
Not for these machines. The sensor is part of the hotend assembly, which is why the replacement is the whole unit.
What reading confirms it?
An open circuit at the hotend connector, against about 100k ohm on the healthy side.
Why will the printer not let me override it?
Because a heater with no temperature feedback has nothing to stop it. That is the one risk the firmware will not take.
LayerWalker
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