Hotend temp not matching

What happened? 

The Original Prusa MK3.5/S continuously monitors the temperature of the tool head in use and its variation with respect to an expected reference. In case the printer recognizes a variation out of the acceptable range, it will display the following message: "Measured temperature is not matching expected value. Check if the thermistor is in contact with the heaterblock. In case of damage, replace it". 

Error name: Hotend temp not matching 

Error code: #28210 (MK3.5S) #23210 (MK3.5)

In this case, the printer will stop the heating and display the message on the screen. The printer then waits for the user to inspect all parts and fix the issue. 

How to fix it? 

1. Make sure that the ambient temperature where the printer is stable, and above 10 ºC.
2. Make sure that your hotend assembly is correct, especially if there have been recent interventions or maintenance. 

   

3. Visually check the thermistor if it is still securely and correctly installed in the heater block. The whole cartridge should be inside the block, with no part of it sticking out.
   
4. Make sure the thermistor and heater are properly plugged into the electronics board. Refer to Step 18 from the linked guide to verify the connections. 
5. Check if the fuses are not blown.

If the issue persists, the error likely stemmed from an issue with the hotend thermistor or, more rarely, hotend heater.