Fans not working



  • Hey Guys,

    I just got my DuetWifi and none of the fans appear to be working. Neither of the always on fans or PWM controlled fans seem to work.

    If I move the fan select jumper to the 5V setting the always on fan pins read correctly (at 5v), but I use 12v fans for everything so this does me no good..

    I read this thread in my search for answers:
    https://www.duet3d.com/forum/thread.php?id=4503#p39340

    In this thread it's suggested that:

    You probably shorted out one of the fan connections or connected a fan with the black and red wires the wrong way round;, and that caused the trace between the VIN pin of the fan voltage selector jumper and +VIN on the power input terminal block to fuse. You can check that with a multimeter. If you find there is no continuity between those points, you can bypass that trace with a wire on the back of the board.

    Can anyone clarify the second part of the comment for me?

    I understand the word "fuse" to mean "connect", so if the Fan Jumper Select VIN pin has been fused with the +VIN terminal on the power in block… then I should see continuity between the two. But instead the comment suggests that if I do NOT see continuity between those points then I need to solder a wire to "bypass a trace". Maybe I have a misunderstanding with the terminology, but right now that seems contradictory - so I'd like some guidance.

    To sum up I have three questions:

    What should the voltage read on the "vFan Jumper Select" vin-pin be?
    What pins should I be testing for continuity between in this scenario to test if something is messed up? (vfan select vin and power in vin?)
    If I get a reading on this in contradiction to what it should be - what two pins should the wire jumper be between to bypass the issue?

    Thanks in advance for any help you can provide.


  • administrators

    The verb "to fuse" has more than one meaning in English. One meaning is "to connect with a fuse". Another meaning is "to burn out due to excessive current" (which is what happens when a fuse blows). That's the meaning I intended in my reply. I suspect that part of the trace has burned out, and if that is the case it needs to be bypassed.

    The pins to connect are the VIN pin on the fan voltage selection jumper block, and the + pin on the VIN power input terminal block. Use a multimeter to check whether there is continuity between these pins first - if there is, then the trace has not burned out.

    HTH David



  • Thank you very much for clarifying that for me!

    Based on your description I was able to test and confirmed that the trace between the vfan select and power in Vins had fused.

    I temporarily connected a wire directly from an available 12v output on the PSU to the V_FAN pin on the fan select jumper block and the fans began to work again.

    Out of curiosity is this a viable long term solution (if I have no interest in powering 5v fans)? Or would you recommend soldering a jumper directly from the Power In terminal to the VIn pin (and subsequently using the jumper)?

    EDIT:

    Saw my question answered in another thread. For anyone that finds this in the future; the answer is yes, you can connect 12v directly to the v_fan header of the Fan Select pin block to bypass a fused trace.

    Thanks for your assistance!



  • I just had this same issue. I bought a Duet Wifi and set everything up this week but I couldn't get any of the fan pins to work right out of the box. All of the fans were wired up correctly and I was careful not to mess anything up while plugging everything in, so I don't see how anything could have shorted.

    I checked for continuity between the 12v terminal and the VIN pin on the jumper block using a multimeter and that turned out to be the issue, and after connecting them with a wire the fans now turn on properly.

    Very annoying, but at least it's an easy fix.


  • administrators

    The latest PCB version (1.03) of the Duet WiFi/Ethernet has a fuse in series with that trace.



  • Ok, that's the blade fuse at the bottom of this page (https://duet3d.dozuki.com/Wiki/Connector_and_spare_part_numbers#Section_Blade_fuse) right? I'll remove the wire and check whether the fuse has gone.

    Thanks for the help.



  • So my multimeter says there's about 0.9MΩ of resistance across the fuse. I think it's safe to say it's probably dead…

    I'll order another one.


 

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