Fault: Fan0 always-on but weird



  • I’m running a DuetWifi 1.02 on 24V with 2x 4010 blower fans (in parallel, each 24V & 0.1A rated) connected to the Fan0 output.

    Unfortunately, after months of perfect printing with it, FAN0 seems to have failed to “always on” somewhat.

    Neither “M106 S0” or “M107” convinced it to turn off.
    The fans are not spinning at full speed - which is a bit odd.
    If I disconnect the fans and measure directly on the board, I get 24V as expected.
    If I connect one fan, it spins slowly, and the voltage reading on the pins drops to about 5.3V…

    My hotend heater and bed heater still work (as the user in the above forum post also had issues with this).
    My hotend cooling fan (FAN1) and my electronics fan (FAN2) all work just fine.
    Both thermistors also show accurate readings.
    If I connect the fans to the FAN1 output they spin perfectly and much faster than on FAN0.

    M122 does not indicate any heater failures or other things.
    VIN is stable between 24.1 and 24.5V.

    Unlike the user in https://www.duet3d.com/forum/thread.php?id=2187#p21356, my board does not show any signs of escaped magic smoke:

    I suspect the MOSFET to have failed short-circuit but not fully? Is this even possible?


  • administrators

    Yes it's possible if the gate oxide has broken down partially.



  • So, do I need to replace the TR5 mosfet (https://duet3d.com/wiki/Connector_and_spare_part_numbers#Fan_mosfet), or is this covered by warranty? I got the DuetWifi in July 2017 from the Duet online shop.


  • administrators

    The warranty is 6 months, so you may just be covered if you submit your claim quickly. See https://www.duet3d.com/warranty.


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