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Bed preheat error

#26201 (MK4S) #13201 (MK4)  # 27201 (MK3.9S) #21201 (MK3.9) #28201 (MK3.5S) #23201 (MK3.5) #31201 (CORE One)

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MK4
MK3.9
MK3.5
MK4S
MK3.9S
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What happened?

The printer is showing the message "Check the heatbed heater & thermistor wiring for possible damage."

Error name: Bed preheat error

Error code: #26201 (MK4S) #13201 (MK4)  # 27201 (MK3.9S) #21201 (MK3.9) #28201 (MK3.5S) #23201 (MK3.5) #31201 (CORE One)

This message is shown when, during the preheat, the printer does not increase more than 2 ºC for 20 seconds. The heating is paused so the issue can be fixed.

How to fix it?

Make sure that the ambient temperature where the printer is is stable, and above 10 ºC.

This error can be caused by damage to either the heatbed thermistor or the heatbed power cable.

Doing regular maintenance on the printer may prevent this type of issue.

On the heatbed, check the following:

  • See if the thermistor is firmly seated below the Golden Kapton tape.
  • Make sure that the washer is screwed above the round cable connector, not below it.
  • Check if the M3nN nut is holding the screw firmly.
  • Access the xBuddy board. Check the heatbed power cable, the heatbed thermistor, and the fuse that protects the heatbed.

In case all the items are correct, there might be an internal break in one of the cables. If you do not have a multimeter, it is possible to check the cables using the following test: 

  1. Use a hairdryer to blow hot air at the heatbed.
  2. While doing that, check if there is any temperature change on the LCD screen.
  3. If there is a positive temperature change it means that the heatbed thermistor is working. In this case, the heater is defective.
  4. If there is no change at all, the heatbed thermistor is defective.

Multimeter check

In case you have a multimeter available, it is possible to check the resistance of the cables using the Multimeter usage guide.

 

4 comments

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säm
•
I got the error with my first ptint of a test item after 80%. With the hair dryer the temp goes up so next to check th cables ? Any other tipp?
Reply
Jan Kratochvíl
•

Hello. Please contact our support team.

Reply
James Fingas
•
I would really like a way to disable this error, or at least change the parameters. I'm using the official Prusa Enclosure with the official Prusa filtration system and a standard Mk4, to print with ABS with the heat bed at 105 C for the first layer and 110 C for subsequent layers.
I get this error about half the time, and it's really annoying, especially to my coworkers if I've stepped away from my desk. Often it occurs after the first layer, when the printer is trying to get up to 110 C. When you're already operating at a high duty cycle, the print bed often doesn't heat up by 2 deg C in 20 seconds.
I'm going to try leaving my filtration system off. Maybe that will fix it.
Reply
Meo Tseto
•
Same thing for me with ABS, the solution I found is to turn off the filtering HEPA. Everything is original from Prusa so I am surprise that happen randomly. I did 3 identical print before having this alarm. To confirm it was the issu I just heat the heatbed alone and confirming the temperature can go to 110 degree without the fan, lower the temperature under 100 and activate the fan of the original Prusa enclosure. The alarm came on as soon it reach the 100 degree because with the fan it can't go higher. The printer is in the garage at 14 degree room temperature. 
Reply
Leninade
•
If you have a high enough airflow filter in an enclosure, the bed will struggle to reach its set temperature and trigger this error. I am limited to about 105C with a 120mm blower fan.
Reply
potte
•
This error can also come up if the print sheet is changed to a new, cold one, too quickly. 
Reply
Tornix
•
That's what just happened to me! Thanks for sharing.
Reply