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Last night I finished printing all the parts for my HeroMe Gen 5 hot end. I decided to just chop off the existing fans and then solder on a JST XH connector to make it easy to change the fans over in the future.

I did the part cooling (adjustable) fan first and it was working great. I then did the same for the nozzle/heatsink fan, but when I plugged in the fan it just didn't work. I checked the voltages on the JST connector pins and they were reading 22.8 V. I thought that was odd, because I'm sure when I checked at the board before I installed the fan it was showing 24 V.

I tested the part cooling fan again and it now no longer works. I checked it's pins on the JST connector and the board and it to is showing 22.8 V.

I checked both adjustable fan sockets on the board and both are showing 22.8 V when the fan is set to 100 %.

When I check the voltage on the fans themselves they're showing 1.5 V between the ground and positive. I didn't read this value when it was working, so I'm sure if this is expected. And unless I have a batch of 6 dodgy fans, I think it must be the printer.

Without trying to lead the answer as to why, I have a feeling at some point during the nozzle fan install, after I tested the fan was working by putting the wires straight into the fans JST connector, i.e. before I soldered, I may have touched the 24 V ground and positive wires together when the printer was on, but I'm not certain. But wouldn't this have tripped a fuse and then be showing 0 V?

What have I broken or how can I work out what's broken?

Please note, I don't understand electronics very well, but I checked the continuity of the PSU input + to the Fan + for the nozzle fan. It shows as 1, which I believe means no connection. If I connect - to -, then it reads 0 which I think means good.

So I guess I've burnt a connection between the Fan + and the PSU + if I understand that right?

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  • $\begingroup$ If the connector gets 22.8 V, you have lost a little along the way, that is possible, Are you sure you haven't interchanged (+) and (-), if so the fan will not work and can be damaged. Considering you measure a voltage, the fan should be able to run. $\endgroup$ – 0scar♦ Feb 11 at 10:38
  • $\begingroup$ I have tried both polarities and the fans were working fine. Also, when I put a load on the wire it drops to 0-1.5V $\endgroup$ – djdd87 Feb 11 at 11:06
  • $\begingroup$ Then you have damaged the fans or the PSU. If the fans aren't working, then your hotend or bed won't heat either if the PSU is broken. I've had this happen also once, my PSU failed due to a short circuit. So, can you connect a heater element directly to the PSU? If that doesn't heat up the PSU is broken. Or, if that works, something on the controller board has broken. Note that this fan is constantly on, so you could power it from the PSU directly. $\endgroup$ – 0scar♦ Feb 11 at 12:23
  • $\begingroup$ The bed heats up fine and I have a solid 24V from the PSU. I think I've fried the lane/fuse between between the fan output and the PSU input. And I'm guessing that fuse sits between both the constant fan and the adjustable fan. New motherboard arriving tomorrow. $\endgroup$ – djdd87 Feb 11 at 12:34
  • $\begingroup$ Sounds like this is similar to what's happened to me: reddit.com/r/3Dprinting/comments/kab17q/… I could try putting a wire in, but that would bypass the fuse I'm guessing. For the sake of £30, I'd rather have a safe board. $\endgroup$ – djdd87 Feb 11 at 12:46

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