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Hotend fan fails self test on new MK4.  

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physics
(@physics)
Member
Hotend fan fails self test on new MK4.

My new, factory assembled, Mk4 fails the fan self test for the hotend (heatbreak) fan. During the fan self test the hotend fan visibly and audibly ramps up and at the same time the LCD rpm readout also ramps up to 6000rpm yet it fails the test. In that sense I don't know what actually failed since the fan appears to work fine and the software seems to be talking to it fine which leads me to suspect a false positive for the test failure condition.

I chatted with support for about an hour (forgot to save the chat log) and the last thing we tried was setting the nozzle temp to 250C and watching the fan speed. The fan speed didn't change appreciably during the several minutes of the test (~2100rpm / 22%). The fact that the fan speed didn't ramp up whiled the nozzle was set to max lead them to conclude the fan may be bad and they are sending me another one. However, the heatbreak temp didn't go past 26C during the test which, to me, indicates the fan had no reason to ramp up. My thought is that the hot end didn't warm up much during the short test and the fan would not have been commanded to ramp up. I have not tried a longer test since I'm not sure about any of this and I don't want to damage the printer.

As for what 'I' could have done to the printer in-between factory assembly and the failed test. I built the Prusa enclosure and installed the printer into it which involved moving the power supply and removing the LCD from the printer and reattaching it to the enclosure (unplug/plug ribbon cable). Here is a link to an okay'ish vid of the printer performing and failing a fan test: https://drive.google.com/file/d/1hoVCYtG6x8cRBq0A6_GM3oNzc1nh_eA_/view?usp=drive_link

Posted : 20/09/2023 7:18 pm
delta_sierraa_88
(@delta_sierraa_88)
Member
RE: Hotend fan fails self test on new MK4.

Same for me. Great summary, thanks. 

Posted : 14/11/2023 5:12 pm
delta_sierraa_88
(@delta_sierraa_88)
Member
RE: Hotend fan fails self test on new MK4.

Same problem for me. Here is how I fixed it:

I fixed it by preheating to PETG temps., then when PETG temps. were reached, I ran the Fan Diagnosis and it passed. Immediately thereafter, I ran the Full Self Test again and it passed. 

 

Thanks @physics for the great summary. Hope this helps! Good luck.  

Posted : 14/11/2023 5:33 pm
Sage
 Sage
(@sage)
Member
RE: Hotend fan fails self test on new MK4.

This also worked for me. Same error and this fixed it. 

Posted : 22/12/2023 7:18 am
cwbullet
(@cwbullet)
Member
RE: Hotend fan fails self test on new MK4.

I am not sure why the PETG trick would work, but it is interesting.  Thanks for sharing. 

Any engineers know why this might work?

--------------------
Chuck H
3D Printer Review Blog

Posted : 22/12/2023 11:35 am
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