HMS 0300-0100-0001-0006: heatbed sensor short circuit
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HMS 0300-0100-0001-0006 means the heatbed temperature sensor is reading as a short circuit. A thermistor that reads near zero ohms looks to the controller like a bed at an impossibly high temperature on some designs, or an invalid reading on others. Either way the printer refuses to heat, and that refusal is what is protecting you.
Affected machines: X1 series. This is the opposite of the open-circuit bed sensor fault, and the two are worth telling apart because the causes differ. Open usually means a connector; short usually means the cable or the sensor body.
Where to buy
The cable mimics the sensor
A thermistor is two wires and a bead. It can fail short, but it is far more common for the two wires to touch somewhere along the run, and the run passes exactly where a moving bed flexes it. Chafing through the insulation at a rub point produces a perfect short with a perfectly healthy sensor on the end of it.
The way to separate them is to measure at the sensor rather than at the board. If it reads around 100k ohm at the sensor and near zero at the board, the fault is in the cable between the two, and you have just saved yourself a wrong diagnosis.
Why the printer will not let you override it
Because a bed heater with a bad temperature reading has nothing telling it when to stop. That is the same reasoning the firmware applies to the hotend, and it is the one place where a software override would be genuinely dangerous rather than merely unwise.
Bed will not heat and the printer reports the heatbed sensor as short circuited
Chafed or pinched sensor cable, occasionally a failed thermistor
- Unplug the printer at the wall and let the bed cool completely.
- Find the bed sensor connector and unplug it.
- Measure across the sensor pins at the sensor side. Around 100k ohm cold is healthy; near zero confirms a short.
- If the sensor reads healthy, measure again at the board end to isolate the cable.
- Inspect the cable run where the bed moves, looking for a rub point, a pinch or a crease.
- If the sensor itself reads short, record the code and raise a support ticket, since the sensor is not sold separately.
Note down both readings before you contact support. A sensor that measures correctly with a shorted cable is a different repair from a failed sensor, and saying which you have makes the conversation much shorter.
The open-circuit version is heatbed sensor open circuit, and the consequence when a sensor lies is heatbed over temperature. Our pages on thermistors and bed temperature explain the parts involved.
HMS 0300-0100-0001-0006 FAQ
What should the bed sensor read?
Around 100k ohm at room temperature on these machines. Near zero is a short; infinity is an open.
Can I bypass it to finish a print?
No. A bed heater with no valid temperature reading is the one override that is genuinely dangerous.
Is the cable repairable?
Sometimes, but on a bed that moves it is a repair that has to last millions of flexes. Service is the safer route.
How is this different from the open-circuit code?
Open usually means a connector has let go. Short usually means two conductors are touching somewhere along the run.
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