MOSFET Testing

  • Hi All,

    I have a Duet3D running in a Tevo Little Monster. Upon starting the machine today, I noticed that the always-on hot end fan wasn't blowing, so I probed some of the connections to see if there was a loose wire or if there was another fault. I can't find a wiring fault and I am wondering if the MOSFET went bad? How would I test the MOSFET to inspect for correct operation?


  • @kzamani The mosfets switch the negative side. Make sure it's not the fan, connect it directly to the power supply. Check the fan fuse. No mosfet on the always on fan connectors.

  • administrators

    Always-on fans are not controlled by mosfets. If your Duet is revision 1.03 or later then perhaps you shorted the fan out or connected it the wrong way round, and the 1A blade fuse for the fan has blown.

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