Shorted PWM fan

  • Hi all,
    I recently shorted my Layer Fan (Fan0) after which it wan't working any more.
    After reading on the forum, I replaced the mosfet on TR5 with a PMV40UN2R.
    But it seems it didn't solve the problem. I'm not an electronics engineer so I really have no clue what could be the problem.
    I also tried connecting the fan to Fan1 and Fan2 , sending a command through the G-code console but that also doesn't work. One thing I noticed is when it is connected to Fan1 it will run for a second or so on power-up but won't run when I send a G-code command. Anyone any suggestions?
    Best regards,

  • Fan 1 and Fan 2 default to thermostatic, you have to turn that off first.

    On later versions of the Duet, there is a fuse for the fans.

  • Thx for the tips, I will check that fuse again cause it looked fine.
    Just out of curiosity, how do just re-appropriate the fan not to work with a thermostat? And if that works, do I than have to post process the G-code replacing Fan0 To Fan1? Thx again, grtz

  • the configurator will guide you with the configuration of the fans

  • Hi, I tested the fan fuse on the board and it seems to be fine.
    Is there a way to figure out what is causing my problem?
    The mosfet on TR5 was damaged but is replaced, the other two look okay. Can one be remapped to be Fan 0?

  • Has nobody an idea on how to solve this issue? I replace the fan 0 mosfet and checked the fan fuse. What else could be wrong?

  • administrators

    Replacing the Fan0 mosfet should have solved it, if you didn't damage the traces to it while removing the old one, and the traces didn't fuse when the fan output was shorted, and the new mosfet hasn't been damaged by static charge (small mosfets are static-sensitive). I suggest you check with a multimeter that the source pin of TR5 is connected to ground, the drain pin is connected to the Fan- pin on the Fan0 connector, and the gate pin is connected to R42.

    Using firmware 2.02 and later you can remap Fan0 to one of the other fan outputs, or to the E1 heater output if it is free. First disable the target fan or heater output just as you would to use is as a general purpose output pin, as described at Then use M106 P0 A# to map it, where # is the logica pin number of the target output.

  • thx a lot, now I can probably find out what is wrong.

  • administrators

    FWIW I recall a blown mosfet once where the trace connecting the source pin to ground, or the associated via, had also fused - although that was before we added the 1A fuse. If that has happened to you then you can add a wire link between TR5 source and the grounded end of R24.

  • Hi, thank for the in depth explanation through that I found that my source pin was not properly soldered to ground. Everything working fine again. Thanks for all the answers and everybody's time, reassured me to press on. Greetings

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