Fans stopped working



  • Hi
    I managed to get my P0 fan that draws air over the Duet working, but I couldn't get the hot end fans to work (there are two). No matter what I did, nothing seemed to register. The hot ends heat up and temp sensors all work, but the fans do nothing.

    I tried seeing what voltage was coming to the pins and couldn't get a good reading that made any sense. Then after rebooting, I notice no fans work. Nothing at all on any of the pins.

    What has happened?


  • administrators

    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.

    I advise against trying to put multimeter probes on the pins of a fan output connector with the board powered up, because it is very easy to short the two fan connector pins together.

    Bear in mind that fan 1 defaults to thermostatic mode, so if you want to control it manually you must first disable thermostatic mode.



  • Where do you advise that? I didn't see any such advice on the guides page for fans. It's annoying to break the board so easily, particularly when you're using an existing wiring loom and the print head is fully assembled. I'd have to take it all apart to find out which wire is connected to which terminal - mine are black and white!

    Actually I think this might be more complicated than I thought, as the K8400 uses a PCB on the print head. Although the heaters and sensors seem to work ok through the pcb, the fans don't. Or didn't. Or something. I can see red and black wires from the fans into the green terminals on the pcb, but there's no indication where it comes out on the loom (jumper? beige block of pins) what the polarity is (these are the black & white wires that I might get wrong at the Duet end). I'm not sure, but I think the only purpose of the pcb is light an LED to indicate which hot end is heating.

    So I'm worried even if I solder this wire on, the first time I connect it I might get the wires the wrong way round and break it again. Incidentally, when I heat one of the hot ends, no LEDs come on but they do heat. The K8400 fans are originally always on 100%.



  • Does anyone know what the jumper is for on the Vin for the fans?

    I read on another thread that it was possible to connect the 12V supply to the fan Vin this to get the fans working again. Can anyone help me on how to do this? My power supply is 15V, but I'm hoping that's ok?


  • administrators

    @biscuitlad:

    Where do you advise that? I didn't see any such advice on the guides page for fans.

    On the Warnings - read this first! page. Now at https://duet3d.dozuki.com/Wiki/Warnings.

    I suggest you trace the PCB connections or use a multimeter, to work out where the black and red fan wires go to.


  • administrators

    @biscuitlad:

    Does anyone know what the jumper is for on the Vin for the fans?

    I read on another thread that it was possible to connect the 12V supply to the fan Vin this to get the fans working again. Can anyone help me on how to do this? My power supply is 15V, but I'm hoping that's ok?

    Yes you can feed +12V (or VIN) to the centre pin of the fan voltage selector jumper block, with no jumper fitted.



  • @dc42:

    @biscuitlad:

    Where do you advise that? I didn't see any such advice on the guides page for fans.

    On the Warnings - read this first! page. Now at https://duet3d.dozuki.com/Wiki/Warnings.

    I suggest you trace the PCB connections or use a multimeter, to work out where the black and red fan wires go to.

    Hi, I still don't see where it says you can damage the board by connecting the fans wires the wrong way round. Might I humbly suggest that particular warning is added to the connecting fans guide? It would have helped me, maybe it help someone else too.



  • @dc42:

    @biscuitlad:

    Does anyone know what the jumper is for on the Vin for the fans?

    I read on another thread that it was possible to connect the 12V supply to the fan Vin this to get the fans working again. Can anyone help me on how to do this? My power supply is 15V, but I'm hoping that's ok?

    Yes you can feed +12V (or VIN) to the centre pin of the fan voltage selector jumper block, with no jumper fitted.

    Ok, thanks. I will try this. My supply is 15V, is there a risk I might break something because it's a bit higher than 12V? As you can see, I really don't know anything about electronics and I'm getting nervous of wrecking the board completely!


  • administrators

    Thanks for the suggestion. I have added a warning to https://duet3d.dozuki.com/Wiki/Connecting_and_configuring_fans.


 

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