SE 0.5mm fan wiggling but not turning

Around the beginning of the pandemic I replaced the dead stock extruder on my Taz 6 with a SE 0.5 mm extruder. The installation and firmware update went smoothly, the filament loads, and superficially everything seemed fine.

Problem is that it would stop extruding not far into a print. I thought it was plugging, and kept cleaning, reloading, and adjusting tension to no avail. Never got a good print out of it! But I think the problem is with the hot end fan mounted adjacent to the drive.

Notice in this movie that at full temperature the fan doesn’t turn. It wiggles, but doesn’t rotate though there are no obstructions. The drive gets really hot, the filament softens, and it can’t gain purchase anymore. Also makes the filament difficult to remove since it turns all stretchy, and the tension knob gets too hot to adjust comfortably.

Is this a defective tool head, or maybe a firmware problem? Clearly it’s trying to do something. Any advice or comparable stories would be helpful!

IMO, either the fan is defective, bound up, or isn’t getting enough power. This fan should run continuously when the printer is turned on.

First thing I’d check is for a bind by loosening the screws holding the fan. Second thing I’d check is the voltage at the connector (since with care, one can insert a multimeter probe into the connector (I sometimes use a T-pin, or you can loosen the connector just a bit to stick the probes in). If the voltage is good and the fan isn’t bound up, then I’d replace the fan.

I checked for a bind by loosening and then removing the screws. No luck. It still wiggles. I did note that if I “prime” the fan a little it sometimes starts turning, though at far too low a speed.

I checked the voltage - 4.95V. I checked it also with an oscilloscope in case there was a PWM issue, but it was a nice smooth 5V.

I concluded that it was a defective fan. I had one from a busted extruder, and so I replaced it. It did the same thing - wiggles, or turns slowly if I prime it. I updated the firmware - no dice.

My conclusion is that this is a problem with the Taz6 itself and that the fan is perhaps not getting enough current. Suggestions on how to proceed short of replacing the Taz6 or shipping it back? I’m up for dissecting and replacing a discrete component, though a circuit is always handy before doing that.

As luck would have it, I recently recycled the last of my Taz6 original cartons since this is years old. DOH!

I doubt that you have two “defective” fans. It is most likely a current issue from either high resistance in the wiring or a defective circuit on the controller board. I believe a replacement controller board is under $50 which is probably less than the shipping costs for the whole printer.

I have a 12v power supply and a “programable” buck converter that I can use to test fans (or anything else). You can buy a cheap 4 cell AA battery holder which will provide 6 volts (or 5.4 with rechargeable AA batteries) that will work for testing 5v fans. Buy 2 holders and you can also test 12v fans.

Did some additional tests, including comparisons against a working Taz6. The hot end fan is rated to 25V and in a working Taz6 it receives 20V. No wonder my dead one barely wiggles or turns!

I tried a replacement universal tool head adaptor just in case the one I had was mis-wired, but no dice. I traced the wires back to the main board hoping to spot an obviously fried component. It ends here (see photo), but there’s nothing obvious. 4.95V all the way back to the board. Seems a new board is in order.

There are two fans on the extruder, the always on fan sometimes called the hot end fan but its job is to keep the cold side of the extruder cool. The other fan is the part cooling fan. Its job is to cool the filament extruded from the nozzle. The always on fan is (or should be) a 5V fan. The part cooling fan is a 24v fan which is driven by a PWM circuit. The speed of the part cooling fan is controlled by the gcode command M106.

If the always on fan is a 24v fan being supplied 5v (or 4.95v in your case), then I could understand why it doesn’t spin.