What happened?
This error appears when the printer detects a mismatch between the expected and measured hotend temperature. It means the thermistor may not be correctly reading the actual temperature, which can be due to poor contact, incorrect mounting, or damage. The message shown is: Measured temperature is not matching expected value. Check the thermistor is in contact with hotend. In case of damage, replace it.
Error name: Hotend temp discrepancy
Error code: #31818 (CORE One) #17818 (XL) #26818 (MK4S) #13818 (MK4) #27818 (MK3.9S) #21818 (MK3.9) #28818 (MK3.5S) #23818 (MK3.5) #12818 (MINI)
How to fix it?
This issue usually comes from a loose or damaged thermistor connection to the hotend.
Nextruder hotend. Picture taken on Original Prusa MK4, shows the heaterblock on CORE One, XL, MK4/S, MK3.9/S.
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| Original Prusa MINI/+ | Original Prusa MK3.5/S |
- Remove the silicone sock if installed.
- Check the hotend thermistor wiring for visible damage, disconnection, or poor contact.
- Ensure the thermistor is firmly seated in the heater block. It should be fully inserted and secured with a set screw.
- If the thermistor appears damaged (frayed wires, broken insulation, etc.), replace it with a compatible spare.
- After reseating or replacing the thermistor, restart the printer and preheat the hotend to verify stable temperature readings.
If the problem continues even after verifying the thermistor, there could be a fault in the electronics or the temperature control loop. Contact our Support for further assistance.