HMS 0300-9300-0001-0003: Chamber Sensor Short at Air Outlet
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HMS 0300-9300-0001-0003 means the chamber temperature is abnormal and the heater temperature sensor at the air outlet may have a short circuit. A shorted thermistor reads near zero ohms, which the firmware interprets as a temperature far outside anything physical.
The sensor at the air outlet sits in the hottest moving air in the machine, which is exactly where insulation ages first.
Where to buy
Keep the right thermistor on hand
These are 100K NTC thermistors with a B value of 3950, the same family used in hotends. A ten-pack costs very little and means a dead sensor is a ten-minute job rather than a wait.
Insulate with something that survives the heat
Kapton polyimide tape is what holds and insulates a sensor in a hot air stream. Electrical tape unwinds, leaves adhesive on the sensor and is often what caused the short in the first place.
Terminate it properly rather than twisting
A crimping tool for Dupont and JST contacts lets you remake the connector the sensor plugs into. Twisted joints wrapped in tape are what short out in a chamber that cycles between cold and hot a thousand times.
Then measure before you replace
Unplug the sensor and measure across it cold. Around 100K ohms is healthy, near zero is the short the message names, and open circuit is the other code entirely.
How HMS 0300-9300-0001-0003 differs from an open circuit
A broken sensor circuit at the power supply is HMS 0300-9300-0001-0008. Short and open are opposite failures that both read as an impossible temperature.
What a lying sensor does to the heater
It makes the heater run forever or not at all, which is HMS 0300-9100-0001-000C. How these parts work is covered in printer thermistors and enclosures.
HMS 0300-9300-0001-0003 FAQ
Which sensor is at the air outlet?
The one in the heated air path, not the one on the board.
Can I print without it?
Not with the chamber heater. It is the feedback.
What should it read cold?
About 100K ohms. Near zero means shorted.
Is tape really the cause?
Often. Heat plus the wrong tape equals a bare joint.
Some messages name a sensor when the fault is mechanical. HMS 07FE-4500-0002-0003 means the filament cutter handle has not been released, and a handle that will not come back up is a spring problem until proven otherwise.
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