Get Hotend fan failure when run self test end to end, but when I run fans self test by itself it passes  

RE: Get Hotend fan failure when run self test end to end, but when I run fans self test by itself it passes

I just finished assembling my MK4 today, and I had the same issue during the self test.  Hotend fan spins up and shows 6-7k RPM on the display, yet came up as failed in the test.  I reran the test twice, on the second try it passed.  It seems there's a few other people with this issue.

Ran a test print and the thing worked fine.

RE: Get Hotend fan failure when run self test end to end, but when I run fans self test by itself it passes

I have same problem, tried 10x times and still failed.

RE: Get Hotend fan failure when run self test end to end, but when I run fans self test by itself it passes

I have also the same problem .... any support from PRUSA ???

RE: Get Hotend fan failure when run self test end to end, but when I run fans self test by itself it passes

Hi @jasond1979,

I had the same problem you had, my Mark IV passed all the initial self-tests, but failed the hot-end fan test. From elsewhere I learned that undoing the fan from the heatsink and letting it spin freely will allow it to pass the self-test, which worked for me. I think this is because the self-test does not quite allow enough time for the fan to get up to 7000rpm when it is loaded up pushing air through the heatsink. I'm running firmware 5.0.0. Prusa, perhaps adding a second or two to the self-test would solve this one?

RE: Get Hotend fan failure when run self test end to end, but when I run fans self test by itself it passes

Same issue for my MK4 as well. Hotend fan fails during selftest, but passes when I run the fan test separately.

RE:

Hi all,

I just finished building the MK4 (kit) and experienced the same issue with the full self-test (firmware 5.0.0), but it magically fixed itself after having experienced the following:

1) First self-test failed due to hot-end fan.
2) I removed the top cap of the nextruder and made sure all connectors are connected firmly to the buddy board (pushed a bit here and there, but nothing budged. It seemed all good from the start).
3) Second self-test failed due to hot-end fan (nextruder cap still off). I actually wanted to abort it after the fan test, but had to complete the full self-test. Anyway, it failed.
4) Then, I found I could do the fan test without doing the full self-test ([start menu] > Control > Diagnostics (below Run Full Selftest) > Test Fans). Here, the fan test passed with maxing at 7224 rpm!

Had this not worked, I would have retested Fans only after loosening the fan screws a bit (similar to how the ball bearings could be overtightened). But perhaps it is only a software issue that can be nudged in the right direction through a partial self test of the hotend fan only.

Hope this anekdote will help!

Regards

RE: Get Hotend fan failure when run self test end to end, but when I run fans self test by itself it passes

I just finished building the MK4 (kit) and experienced the same issue,

1) First self-test failed due to hot-end fan, RPM show 0 but the fan is spinning at different speed.

2) I removed the top cap of the nextruder and made sure all connectors are connected firmly to the buddy board.... still failing

3) Did the test without the fan connected and  for sure it failed .

4) I connected the fan again and did a diagnostic test fan and still have 0 rpm and test failed.

What else should i do ?

RE:

IMG_4200Mine did it, slackened off the screws and tightened them EQUALLY, unplugged the cable and re-seated it then gave the centre of the fan a tap. Re-did the startup test and it worked perfectly.

first print off was the bonkers benchy (12 minute one) utterly flawless 

Posted by: @standus

I have same problem, tried 10x times and still failed.

RE: Get Hotend fan failure when run self test end to end, but when I run fans self test by itself it passes

First of all, check that both fans are running when the test starts.

When the hot-end fan test comes up, watch to see if the rpm figures at the bottom of the display are changing. The one on the right should get close to 7000rpm.

If everything else is fine but the hot-end fan test fails, it seems to me that it may not be getting up to speed fast enough. On my printer, I re-ran the test with a credit card held over half the fan, and it passed the test no problems. Stopping some of the air flowing through the fan allowed it to get up to speed faster. The printer has printed fine ever since.

Not everyone is having this problem, so it may be a particular batch of fans that are just failing. Get into a chat with Prusa to see if they will send another hot-end fan.

RE: Get Hotend fan failure when run self test end to end, but when I run fans self test by itself it passes

I finished assembling my MK4 kit today and had the same issue. Hot end fan was spinning, rising to over 7k rpm but was still failing the test.

Multiple power cycles didn't fix it. Taking the cover off the love board and checking cables didn't fix it. Loosening the 2 screws mounting the fan on didn't fix it (but helped fan speed a little). Last ditched attempt whilst waiting for Prusa support, I decided to unplug the cable at the love board end and plug back in, reassemble and test again. Success! Not sure whether it was random chance, but unplugging and plugging in that fan connector fixed it enough for me to pass the self test

RE:

Just unboxed fully assembled MK4 and get Hotend fan failure.
Fails during self test
Fails via Control > Diagnostics > Fan Test where Hotend fan hits 6582 rpm
Updated firmware to 5.0.1 - that did not fix it.

Please advise

Will start this in a new topic as well since different than the title of this thread, the best content I found on the matter.

RE: Get Hotend fan failure when run self test end to end, but when I run fans self test by itself it passes

Figured I'd throw my hat in too, I'm getting the same issue.
 - Self-assembled kit
 - Both fans spinning up and reading RPMs and failing the self-test.
 - Firmware updated to 5.0.1

RE: Get Hotend fan failure when run self test end to end, but when I run fans self test by itself it passes

I had this issue on the first self test after building the printer. It would appear that I had tightened the two fan mounting screws too much. This apparently slightly distorts the fan housing causing the fan to run slowly. I slackened the mounting bolts off slightly and gave the fan a gentle tap to get it to resettle. It then passed the self test first try after this.

RE:

I had the same issue. I contacted support and they told me to flash the printer with Firmware 5.1.0-alpha2. It worked!

I asked if the firmware is stable and they told me that it is and it should be out soon.

RE: Get Hotend fan failure when run self test end to end, but when I run fans self test by itself it passes

Same issue! New mk4, pre-assembled: fan spins fine, but only goes to 6800 RPM or so. I just tried flashing 5.1.0-alpha2 on a new out-of-the-box pre-assembled mk4 and it passed the standalone fan test, but failed in the end-to-end.  

I also checked the connections on the Love Board and they were fine.

Hm!

-j-

RE: Get Hotend fan failure when run self test end to end, but when I run fans self test by itself it passes

This trick (block half the air-flow) totally worked.  I'm only printing PLA so maybe I don't need to worry about the fans too much? In any event: thank you!  I guess I'll write Prusa about it, or see if a future firmware update fixes anything.

RE: Get Hotend fan failure when run self test end to end, but when I run fans self test by itself it passes

Finished my upgrade and was crushed when it failed for hot end fan speed. I doubled checked the screw torque, checked the wiring and re-seated the cable plug. I found that it would pass the fan test if I left it hanging from the wires, mount the fan and it failed, loosened the screws and it passed. lightly tighened the screws and it failed. I cut two paper washers about 5 mm in diameter out of typing paper and put them between the fan and heat sink and tightened the screws as normal and it now passes everytime. FW ver. 5.0.1

RE: Get Hotend fan failure when run self test end to end, but when I run fans self test by itself it passes

I fixed with Prusa support. My problem was that the cables for the 2 fans were swapped.

RE: Get Hotend fan failure when run self test end to end, but when I run fans self test by itself it passes

Thank you this solved the hotend fan issue, as you said took the fan off, the fan could then spool up quicker and pass the test.