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UM2 Side fans always on, centre fan always off.


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Posted · UM2 Side fans always on, centre fan always off.

Hey everyone,

Apologies if this has already been mentioned, I did use the search function but either I'm doing it wrong or it's not there.

The other day my UM2 seemed to short out, after I'd checked everything to make sure nothing had blown I turned it back on and the side fans are acting like they're on 100% permanently. There's just no way of controlling them. Is there anything I can do to sort this without having to resort to a new board? Everything else works fine, it prints absolutely great still, just the fans are annoying when the printer is idle.

Also, for as long as I can remember the centre cooling fan doesn't work, I tried replacing the fan but that's made no difference.

Please help!

Thanks in advance x

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    • 4 weeks later...
    Posted · UM2 Side fans always on, centre fan always off.

    Better late than never, I suppose?


    Sometimes questions begs more questions, and this is one of those times, I'm afraid.


    It's a straight UM2, not a 2+? Regardless, it would be best if you check which main board version you have. It'll say so in the silk screen on the component side of the PCB.


    Assuming it's a 2.1.1 and the printer is alive at least (you can make it do things), the hot end fan problem cannot be located on the board, as the 2.1.1 supplies constant +5V directly from the onboard power supply to the fan (except if we're talking copper / connector problems). If the fan isn't running and the problem is on the board, the entire printer would be dead as a hammer. Since you've replaced the hot end fan itself, I'm going to go ahead and assume there's a problem with the fan extender cable in the loom to the head.


    The model fans, on the other hand, is extremely likely to be board failure. Regardless of board revision, they're PWM controlled. I'll bet you just about anything that T1 is shorted collector-emitter. Thankfully, if you're handy with a soldering iron or know someone who is, you can get spare transistors thrown at you everywhere. It's a BC817. As you can see, they're certainly affordable enough and stock is never a problem.




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