- 3D printers
- 3D printer
13203
Prusa 13203 on a MK4 3D printer: bed thermal runaway
Risk level
High
Professional inspection is recommended.
Urgency
High
Quick answer
Prusa error 13203 on the MK4 is the bed thermal runaway protection: the temperature dropped more than 2 °C for over 60 seconds and the printer stopped. Check the room for draughts and the bed thermistor.
Safety first
Stop and check this first
- Do not disable or bypass the thermal protection or change the firmware to clear the alert: it is what cuts the heat when the temperature does not add up. Do not open the printer's power supply or mains board: anything at mains voltage is for the service team.
- Prusa asks for the printer to be cooled down and switched off before you access any part or electronic board. The nozzle and the bed burn while they are hot.
Safe checks you can perform
- Stable room temperature
- Thermistor under the Kapton tape
- Small parts in high temperature filaments
Leave these tasks to a qualified professional
- Do not attempt this professional task: Bed cables in the electronics box
- Do not attempt this professional task: Multimeter measurement
- Do not attempt this professional task: Case with Prusa support
What a technician must be able to justify
Technician visit
These are the steps they must carry out and show you. Tick them as they work: if steps are skipped, do not accept a part swap.
These are not instructions for opening or handling the equipment yourself. They are the checks that should support a technical conclusion.
Bed cables in the electronics box
What they doThe technician opens the xBuddy box and electronics box covers and checks that the bed power cable has not slipped from its screw and that the thermistor cable is properly connected.
They must show youboth cables secured.
In writingwhat was checked and corrected.
Multimeter measurement
What they doThe technician measures the resistance of the bed cables following the multimeter usage guide Prusa links to.
They must show youthe values measured against Prusa's guide.
In writingthe readings and the part replaced.
Case with Prusa support
What they doPrusa's 24/7 technical support guides the check of the bed or arranges the part if needed.
They must show youthe steps they ask for and why.
In writingcase number and part sent.
Before accepting a part or repair
Nothing has been shown yet. Do not accept a part swap based on the code alone.
Follow these steps
Note: Follow the documented order. An error code identifies the affected system, but it does not prove by itself which part has failed.
Stable room temperature
- Who:
- you.
- How:
- look at where the printer sits: Prusa asks for a stable ambient temperature above 18 °C, with no cooling sources nearby such as air conditioning or windows.
- Result that matters:
- whether the room is cold or draughty.
- If it is cold or draughty:
- move the printer or fix the room before trying again.
- If the room is fine:
- the cause is in the printer.
- Evidence to keep:
- room temperature and time.
Evidence: Prusa Knowledge Base: Bed thermal runaway #31203 (CORE One) #35203 (CORE One L) #36203 (CORE One INDX) #26203 (MK4S) #13203 (MK4) #27203 (MK3.9S) #21203 (MK3.9) #28203 (MK3.5S) #23203 (MK3.5)
Thermistor under the Kapton tape
- Who:
- you.
- How:
- with the bed cold and the printer off, check whether the bed thermistor is still held firmly under the golden Kapton tape, without touching or lifting the tape.
- Result that matters:
- whether the thermistor is in place.
- If it looks loose or lifted:
- tell support or the technician.
- If it is held firmly:
- the cause is in the cables or the thermistor.
- Evidence to keep:
- photo of the thermistor.
Evidence: Prusa Knowledge Base: Bed thermal runaway #31203 (CORE One) #35203 (CORE One L) #36203 (CORE One INDX) #26203 (MK4S) #13203 (MK4) #27203 (MK3.9S) #21203 (MK3.9) #28203 (MK3.5S) #23203 (MK3.5)
Small parts in high temperature filaments
- Who:
- you.
- How:
- if you were printing small objects in a high temperature filament, try printing several at once or placing them away from the centre of the bed, as Prusa suggests.
- Result that matters:
- whether the error stops with that layout.
- If it stops:
- it was heat loss in that area.
- If it continues:
- the cause is in the cables or thermistor.
- Evidence to keep:
- screenshot of the job in the slicer.
Evidence: Prusa Knowledge Base: Bed thermal runaway #31203 (CORE One) #35203 (CORE One L) #36203 (CORE One INDX) #26203 (MK4S) #13203 (MK4) #27203 (MK3.9S) #21203 (MK3.9) #28203 (MK3.5S) #23203 (MK3.5)
Still not solved
If the error persists, stop here. See what the technician must do and show you.
Where this code applies
A code is meaningful only inside the right product and version context.
Primary scope
- System
- 3D printers
- Brand
- Prusa Research
- Product type
- 3D printer
Known code variants
- #13203
- 21203
- 23203
- 26203
- 31203
- Bed thermal runaway
- Deriva térmica base
- Prusa 13203
What it means
Prusa explains that thermal runaway is a safety feature that cuts power to the heaters if a cable fails. If the thermistor comes loose, the electronics read a lower temperature than the real one and, to compensate, the heater could reach dangerously high temperatures. If the bed temperature drops by more than 2 °C for over 60 seconds, the printer stops the print and shows the error. It is 26203 on the MK4S and 31203 on the CORE One.
Warnings and stop conditions
- Criticaleditorial warning
Do not disable or bypass the thermal protection or change the firmware to clear the alert: it is what cuts the heat when the temperature does not add up. Do not open the printer's power supply or mains board: anything at mains voltage is for the service team.
Evidence: Prusa Knowledge Base: Bed thermal runaway #31203 (CORE One) #35203 (CORE One L) #36203 (CORE One INDX) #26203 (MK4S) #13203 (MK4) #27203 (MK3.9S) #21203 (MK3.9) #28203 (MK3.5S) #23203 (MK3.5)
- Highsource verified
Prusa asks for the printer to be cooled down and switched off before you access any part or electronic board. The nozzle and the bed burn while they are hot.
Evidence: Prusa Knowledge Base: Bed thermal runaway #31203 (CORE One) #35203 (CORE One L) #36203 (CORE One INDX) #26203 (MK4S) #13203 (MK4) #27203 (MK3.9S) #21203 (MK3.9) #28203 (MK3.5S) #23203 (MK3.5)
Symptoms and causes
Probable causes · in order
- Cold or draughts near the printerPossible
A room below 18 °C or cooling sources nearby, such as air conditioning or windows, can cool the bed faster than it recovers.
Evidence: Prusa Knowledge Base: Bed thermal runaway #31203 (CORE One) #35203 (CORE One L) #36203 (CORE One INDX) #26203 (MK4S) #13203 (MK4) #27203 (MK3.9S) #21203 (MK3.9) #28203 (MK3.5S) #23203 (MK3.5)
- Loose bed thermistorPossible
If the thermistor has come loose from under the Kapton tape, it reads less than the real temperature; it is the case the protection is there to stop.
Evidence: Prusa Knowledge Base: Bed thermal runaway #31203 (CORE One) #35203 (CORE One L) #36203 (CORE One INDX) #26203 (MK4S) #13203 (MK4) #27203 (MK3.9S) #21203 (MK3.9) #28203 (MK3.5S) #23203 (MK3.5)
- Power or thermistor cablePossible
If the bed power cable has slipped from its screw or the thermistor cable is badly connected, the bed loses heat or reading.
Evidence: Prusa Knowledge Base: Bed thermal runaway #31203 (CORE One) #35203 (CORE One L) #36203 (CORE One INDX) #26203 (MK4S) #13203 (MK4) #27203 (MK3.9S) #21203 (MK3.9) #28203 (MK3.5S) #23203 (MK3.5)
Virtual technician
Does 13203 still appear after these checks?
Answer a few questions to narrow down the likely cause and the safest next action. Guidance only - it never replaces a professional.
Sources and technical references
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