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P
12203
Moderate
Prusa · FDM 3D Printers
THERMAL_RUNAWAY Hotend - Temperature Deviated Beyond Safe Range
Quick Answer
Error code 12203 on your Prusa FDM 3D Printers means: THERMAL_RUNAWAY Hotend - Temperature Deviated Beyond Safe Range. This is usually fixable — see the step-by-step guide below.
Affected Models
Applies to all models
MINI+MK3.5MK3S+MK4MK4SXL
Likely Causes
  1. Part cooling fan blowing directly on the heat block due to incorrect fan shroud installation
  2. Silicone sock missing from heat block causing excessive heat loss
  3. Heater cartridge seated loosely in the heat block
  4. PID values were reset after firmware update and need re-calibration
  5. Printing in a cold environment with drafts causing erratic temperature swings
How to Fix It
1
Check that the silicone sock is properly fitted on the heat block
2
Verify the heater cartridge is firmly seated with the retention screw tightened
3
Run PID calibration from the printer menu: LCD > Settings > Temperature > PID Calibration
4
Ensure the print fan shroud is correctly installed and not directing air onto the heater block
5
If printing in a cold room, consider adding a draft shield or enclosure
Pro Tip
This fix requires some technical knowledge. If you're unsure about any step, consider contacting support or a qualified technician.
Parts You May Need
Silicone sock for E3D V6 or Nextruder (model dependent)
Heater cartridge (40W for MK3S+, 50W for MK4/MK4S)
Printer enclosure (Prusa original or third-party)
Related Error Codes
1220112202122111221212213
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