Printer reboots mid print / Heatbed Thermistor breaks at 150mm from bed?
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Printer reboots mid print / Heatbed Thermistor breaks at 150mm from bed?  

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Printer reboots mid print / Heatbed Thermistor breaks at 150mm from bed?

Note: I'm working with Prusa support and QC. I'm posting this in case others come across a similar problem.


  1. Printer reboots in middle of print
  2. Previously had a 12203 or 12204 Thermal Runaway error - I had just got the printer and didn't take a photo (this occurred only once, and may have been related to the hotend thermistor, which also needed replacement) 

Failed tests:

  1. Printer reboots when preheating bed 
  2. If printer does not reboot,
    1. Printer reboots when heatbed cable bundle moved
      1. Specifically if it's bent around 150mm (as measured from heatbed)
        1. Video preheat
        2. video tap cable
  3. Temperature on Display
    1. if temp on display shows accurate room temp - printer will not reboot
    2. if display temp is at 0, printer will reboot
  4. Multimeter resistance test - multimeter set at 200k
    1. Cable appears to pass resistance test -reads circa 112
    2. Cable fails resistance test when bent circa 150mm (shows 1)
    3. When moved cable will switch to alternate to pass/fail

Mixed results:

  1. Heatbed power cables 
    1. Could be user error

Passed tests:

  1. Cable bundle visual inspection
  2. Cable connections visual inspection
  3. Heatbed thermistor visual inspection
  4. Buddy board visual inspection
  5. Preheating nozzle
  6. Seating the Heatbed thermistor in the nozzle Thermistor location -
    1. Nozzle thermistor display (connected to heatbed thermistor) shows 0 or accurate temp as above failed tests 
    2. Heatbed thermistor display (connected to nozzle thermistor) shows accurate temp
  7. Multimeter resistance tests: hotend thermistor and power cable Pass
  8. Fuses both pass continuity tests
  9. Probably a bunch of others.

Attempts at resolution:

  1. Round 1: 1/23/23
    1. Assumption: Heatbed power cable faulty 
    2. Replaced Heatbed power cable
  2. Round 2: 1/27/23
    1. Assumption: Thermistor(s) and heatbed faulty 
    2. Replaced Heatbed
      1. Including Thermistor and Power cable
    3. Replaced hotend Thermistor (may or may not be related)
  3. Round 3: 2/13
    1. Note: Tech had to confer offline with colleagues and Quality Control
    2. Assumption: Buddy board may be faulty > which may be causing issues with the heatbed (and possibly the hotend thermistor)
      1. New Buddy board will be sent to me
      2. I will send to Quality Control for inspection:
        1. Original Buddy Board
        2. The Original heatbed
          1. The attached Heatbed Thermistor
        3. Original heatbed power cable
        4. Original Hotend Thermistor


POSSIBLE ERROR IN SUPPORT PAGES - anyone know how to get them reviewed?

12203 says range for heatbed is 6.5-7  (this seems to be in error)

The main multimeter article shows heatbed at 4.5-6.5 (this seems to be correct).



This topic was modified 1 year ago 2 times by SirHair
Posted : 15/02/2023 5:27 am