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UM3 Front Fan not working.

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Last month I was investigating reasons why a Front fan on one of our Ultimaker 3's was not functioning. I experimented with other printers figuring out that at 40-50 degrees C on the heat block, the front fan will kick on and keep the print core cool. So I replicated this for the printer with the broken fan and found the fan would not operate. I detached said fan and tested it in other printers and found that it works as it should. Upon further investigation, I found that a Resistor (R1, my guess at least) on the print head board was disconnected and hanging by a solder joint. We had a skilled solderer re-solder the resistor back on. I recently tried to use the print head again and found that the front fan is still not operating. So what I know is:
  • Front fan itself functions (just not attached to suspect print head)
  • Resistor is set on the board again (R1 for reference)
  • The print head cable functions as should. *Tested with other prints head*
  • There appears to be no physical damage to the board. The only aspect I have suspicion of is what appears to be a transistor. During inspection of a working board and the one in question, I found that a transistor seems to be bent at an angle.
  • I used a multimeter and found no voltage on the front fan plug-in on the board while I got readings for the rest. 


Any recommendations on my next move? I know where I can buy a replacement board but I would rather fix this one if at all possible. My guess is that there is something wrong with the print head circuit board.

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3 minutes ago, Nicolinux said:



have you tried attaching a working front fan door (with the circuit board) to the printer with the seemingly faulty board? This way you could rule out the circuit board on the fan door.

I have not but I will give it a try. 

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