- 3D printers
- 3D printer
13204
Prusa 13204 on a MK4 3D printer: hotend thermal runaway
Risk level
High
Professional inspection is recommended.
Urgency
High
Quick answer
Prusa error 13204 on the MK4 means the nozzle dropped 12 °C and did not recover heat within 60 seconds, so the printer cut heating. Let it cool, check the room and that the thermistor is still fully inserted in the heater block.
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
- LoveBoard cables in view
- Silicone sock and heater block
Leave these tasks to a qualified professional
- Do not attempt this professional task: Multimeter measurement
- Do not attempt this professional task: Thermistor fully inserted in the heater block
- Do not attempt this professional task: LoveBoard cables, fuse and main cable
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.
Multimeter measurement
What they doThe technician measures the resistance of the hotend heater and thermistor 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.
Thermistor fully inserted in the heater block
What they doThe technician removes the silicone sock, reaches the set screws and checks the thermistor is fully inserted in the block and not loose.
They must show youthe seated thermistor.
In writingwhat was adjusted.
LoveBoard cables, fuse and main cable
What they doThe technician checks the heater and thermistor cables at the LoveBoard, the fuse protecting the extruder on the xBuddy board and that the LoveBoard main cable is properly connected and not pinched.
They must show youthe state of cables and fuse.
In writingwhat was checked and replaced.
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.
- 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: Hotend thermal runaway #31204 (CORE One) #35204 (CORE One L) #26204 (MK4S) #13204 (MK4) #27204 (MK3.9S) #21204 (MK3.9)
LoveBoard cables in view
- Who:
- you, if you follow Prusa's guide for your model.
- How:
- with the printer cold and off, access the LoveBoard (on the MK4 the cover slides upward) and check whether the heater and thermistor cables are properly connected and undamaged along their length.
- Result that matters:
- seated connectors and uncut cables.
- If you see a loose connector:
- reseat it with the printer off.
- If you see a damaged cable:
- do not repair it yourself; ask for the part.
- Evidence to keep:
- photos of the LoveBoard and cables.
Evidence: Prusa Knowledge Base: Hotend thermal runaway #31204 (CORE One) #35204 (CORE One L) #26204 (MK4S) #13204 (MK4) #27204 (MK3.9S) #21204 (MK3.9)
Silicone sock and heater block
- Who:
- you, looking only.
- How:
- with the nozzle cold and the printer off, check that the silicone sock is fitted and that the thermistor and heater look secure in the block. Do not loosen the set screws.
- Result that matters:
- whether anything looks loose or out of place.
- If something is loose:
- have the technician or support check it.
- If everything looks in place:
- the cause is in cables or parts.
- Evidence to keep:
- photo of the heater block.
Evidence: Prusa Knowledge Base: Hotend thermal runaway #31204 (CORE One) #35204 (CORE One L) #26204 (MK4S) #13204 (MK4) #27204 (MK3.9S) #21204 (MK3.9)
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
- #13204
- 21204
- 26204
- 31204
- Deriva térmica hotend
- Hotend thermal runaway
- Prusa 13204
What it means
Prusa explains this error shows if the nozzle temperature drops by 12 °C for an extended time. That drop is not usually a problem, but if the heat is not recovered within 60 seconds, the printer stops heating and shows the message. The cause can be any damage to the hotend heater or thermistor; Prusa asks you to check that the thermistor is fully inserted in the heater block, the cables at the LoveBoard, the extruder fuse and the main cable. It is 26204 on the MK4S and 31204 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: Hotend thermal runaway #31204 (CORE One) #35204 (CORE One L) #26204 (MK4S) #13204 (MK4) #27204 (MK3.9S) #21204 (MK3.9)
- 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: Hotend thermal runaway #31204 (CORE One) #35204 (CORE One L) #26204 (MK4S) #13204 (MK4) #27204 (MK3.9S) #21204 (MK3.9)
Symptoms and causes
Probable causes · in order
- Thermistor loose in the heater blockPossible
If the thermistor is not fully inserted in the heater block or has come loose, it reads less heat than real and the protection triggers.
Evidence: Prusa Knowledge Base: Hotend thermal runaway #31204 (CORE One) #35204 (CORE One L) #26204 (MK4S) #13204 (MK4) #27204 (MK3.9S) #21204 (MK3.9)
- Damaged hotend heater or thermistorPossible
Any damage to the hotend heater or thermistor can stop the temperature recovering in time.
Evidence: Prusa Knowledge Base: Hotend thermal runaway #31204 (CORE One) #35204 (CORE One L) #26204 (MK4S) #13204 (MK4) #27204 (MK3.9S) #21204 (MK3.9)
- LoveBoard cables, fuse or main cablePossible
Damaged cables at the LoveBoard, the extruder fuse on the xBuddy or a pinched main cable also cause the error.
Evidence: Prusa Knowledge Base: Hotend thermal runaway #31204 (CORE One) #35204 (CORE One L) #26204 (MK4S) #13204 (MK4) #27204 (MK3.9S) #21204 (MK3.9)
Virtual technician
Does 13204 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
- 1
Prusa Research · 2026 · official_doc
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