HMS 0300-9100-0001-0003: chamber heater over-temperature
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HMS 0300-9100-0001-0003 means the chamber heater itself went over temperature and its protection cut in. The distinction that matters is where the heat was: not in the chamber, which may well have been cold, but at the element. A heater only cooks itself when the air that should carry its heat away is not moving, or when something tells it to keep heating a chamber that is already warm.
Affected machines: H2D and the X1 series. A chamber heater is a resistive element with a fan behind it, and the design assumes the fan works. Break that assumption and the element sees its own heat instead of the chamber, which is exactly what the cutout is there to catch.
Where to buy
Airflow first, sensor second
Look for anything blocking the heater vents. Purge waste that has fallen behind the plate, a filter that has turned into a felt mat, and dust bound together with filament residue are the three usual finds, and a torch makes all three obvious in a way that feeling around does not.
Then check the fan on that path actually spins. A heater fan that has slowed is enough on its own, and it will not necessarily have reported its own fault first.
If the airflow is genuinely clear, suspect the sensor. A chamber sensor reading low makes the controller believe the chamber is cold, so it keeps the element on long past the point it should have backed off. The heater cooks, the protection trips, and nothing looks blocked because nothing is.
Chamber heating stops and the printer reports the heater is over temperature
Blocked heater vent or a stalled fan, or a chamber sensor reading lower than the real temperature
- Power off at the wall and let the chamber cool fully before opening it. The heater area stays hot.
- Inspect the heater inlet and outlet vents with a torch, and remove anything sitting against them.
- Clean or replace the chamber filter if your model has one on that path.
- Confirm the fan on the heater path spins freely by hand and starts when the machine powers up.
- Measure the chamber sensor cold. Around 100k ohm is healthy; a reading well below that makes the controller overheat the element.
- Run a chamber preheat and watch the temperature climb steadily rather than stalling or spiking.
Do not clear the code and run again to see whether it holds. An over-temperature cutout on a heating element inside a closed box is the one protection on a 3D printer that is standing between you and a fire.
The vent-specific version is chamber heater control abnormal with a blocked vent, and the sensor version is chamber sensor open circuit. Our page on enclosed printers explains what chamber heat does, and the troubleshooting index covers the rest.
HMS 0300-9100-0001-0003 FAQ
Can I print PLA while this is unresolved?
Yes. PLA does not use chamber heating, and the machine will run without it.
The chamber was cold. How can the heater be over temperature?
Because the measurement is at the element, not in the room. No airflow means the element cooks while the chamber stays cold.
What should the chamber sensor read?
Around 100k ohm at room temperature. Well below that and the controller is working on bad information.
Is it safe to keep resetting it?
No. Repeatedly clearing a thermal cutout is how a protected fault becomes an unprotected one.
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