Print fan working, reporting RPM, but test failing?
 
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Print fan working, reporting RPM, but test failing?  

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Michi Lumin
(@michi-lumin)
Member
Print fan working, reporting RPM, but test failing?

MK4 with input shaper firmware alpha.

Ran a self test today and the print fan reports as failed every time.
But I can't figure out why.  (Other fan passes fine.)

The printer is maybe 3 weeks old.

  • The fan spins freely.
  • The RPM is obviously being reported  in sensor status.
  • I can go into temperature controls and go from around 3% - 100% which gives me an RPM range of 2750 - 6875 RPM. 
  • When the print fan is off, RPM for the print fan reads 0.

Just in case I tried making sure it was plugged in properly to the LoveBoard, and that the yellow wire wasn't damaged; all is OK there (and again it is reporting RPM just fine.)

I blew the print fan out with compressed air just in case, as well.  (it really has no resistance when spinning, it isn't blocked.)

Any ideas what this could be?  It doesn't seem to be a connection issue of any sort.

 

This topic was modified 7 months ago by Michi Lumin
Posted : 08/08/2023 11:04 pm
Sephzer
(@sephzer)
New Member
RE: Print fan working, reporting RPM, but test failing?

I had the same issue this morning, I just unplugged the fan and re-plugged it, made sure the cables weren't too tight and then it passed.

Posted : 04/09/2023 1:01 pm
ProBucketHead
(@probuckethead)
Member
RE: Print fan working, reporting RPM, but test failing?

@michi-lumin did you find a solution to this?

Posted : 12/11/2023 1:49 am
Pete Hillyer
(@pete-hillyer)
Member
RE: Print fan working, reporting RPM, but test failing?

I had this same issue on a recently assembled mk4. 

After speaking to support they confirm that is an issue being worked on. 

in my opinion it is caused by two issues. 
the airflow resistance from the fan through the heatsink is causing the fan to slow down a little below 7000 rpm. And the firmware rpm threshold is set at around 7000 rpm, which may be a little too tight. 

i found that removing the fan and holding it while doing a test repeatedly passed. 

as a workaround i added a 3mm plastic washer on both fixing screws between the fan and the heatsink assembly. This allows a little more airflow to escape behind the fan and hence speed it up just enough. 

Posted : 14/11/2023 3:01 pm
alpritt
(@alpritt)
Active Member
RE: Print fan working, reporting RPM, but test failing?

I have the exact same issue with similar RPM. I also tried the washer trick and that made the test pass, but I'm not sure if the gap affects the performance of the cooling or not. I haven't actually tried to print yet. 

I was asking support about it but the Live Chat got cut off and there was a long queue so I emailed them and am waiting to hear back.

Posted : 22/11/2023 6:48 pm
steve457
(@steve457)
Eminent Member
RE: Print fan working, reporting RPM, but test failing?

I've run into this same problem on one of my MK4 (the other is fine for whatever reason), and support even sent me a new fan as my other fan did sound a bit odd as if it was struggling. Even with the new fan I get a failure unless I loosen the two fan screws quite a bit so the fan wiggles around and is loose. In any case, I just end up doing the test with the fan completely loose and then tighten it back down after the test is done. It doesn't seem to have any negative impact on testing, but would like to see an official response from Prusa if this error is expected or not.

Posted : 23/11/2023 7:22 am
bbmester
(@bbmester)
Member
RE: Print fan working, reporting RPM, but test failing?

Same  issue.

Printfan failed selftest. Fan is spinning freely from 29 to 7843 rpm, when testing. Tried removing fan to let it test in free air, no help. Checked wires, no breaks.

Is it a software problem?

Posted : 23/11/2023 8:11 am
Mark Casey
(@mark-casey)
Member
RE: Print fan working, reporting RPM, but test failing?

Same issue here

Posted : 23/11/2023 10:04 pm
FamousMamous
(@famousmamous)
Member
RE: Print fan working, reporting RPM, but test failing?

I was having the same issue. Hotend fan RPM test would fail during initial setup. It would still fail with the fan removed from the heatsink assembly as suggested above. During the test I lightly blew on the fan to get a few extra RPMs. That was successful. Definity not ideal but at least it does not ask for the initial setup when I turn the printer on anymore.

Posted : 24/11/2023 2:25 pm
Moyrn
(@moyrn)
Active Member
RE: Print fan working, reporting RPM, but test failing?

Hello. exactly same issue here. Just opened a case

https://github.com/prusa3d/Prusa-Firmware-Buddy/issues/3515

I was on 4.4.0 all fine since months.I wanted to test input shaperSo i did the 4.4.1 upgrade as recommended, instantly followed by 5.1.0

All went fine(My settings for Bondtech E were still there fine Z190 E412 Reverse)

First print failed after layer 1

impossible to print : print fan error <<

Self test is KO on the printer fan, all is okthe printer fan is running fine ; and i printed for years all fine until nowi tried a factory reset... no change

if i remove the fan check : i can print fine

Posted : 24/11/2023 8:42 pm
Moyrn
(@moyrn)
Active Member
RE: Print fan working, reporting RPM, but test failing?

Strange thing : I removed the print fan and the self-test was still KO - though RPM still reportingI then noticed the yellow wire was quasi loose. touching it and it was brokeni then resoldered it, and made another self test in free air : passed OK - reporting something like 7800RPMi mounted it back fully : passed OKI renabled "check fan"I launched a print : passed OK

So possibly a pinched or loose cable in my case. Firmware is just performing tests which were not there before. 

Posted : 24/11/2023 9:41 pm
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