[PROBLEM] Hot end error after terminals broke off fan

Hi, I got a Prusa i3 kit a few weeks ago from China. It was $240 so obviously many parts were sub-par quality or were easily broken from over-tightening a screw, Not to mention the power supply provided couldn't supply enough current to power our hot bed.

Anyways, my current issue is that somehow I have ripped the terminals off my extruder fan (cold end fan) while adjusting the E motor gear. It was a 12V 0.1A brushless DC fan. Because of this I now have an error on my LCD in the temperature readout. It says (def / 185) for hot-end and (def / 50) on the bed. 185 and 50 could be whatever I set the temperatures to. The hot end and bed do not heat up at all.

I bought a 12V 0.13A brushless DC fan and replaced the old one. Now it will send three short pulses to the fan upon power on of the machine and the controller can detect that it's not the same fan so I am still in the same rut.


Can I change firmware settings to allow me to print without this secondary fan? I can set up an external fan on the table next to my machine but I can't wait a month for the exact same fan from China.

I fear that the fan issue and the "def" error are unrelated if you have any insight I would greatly appreciate it!

The controller can't detect the type of fan... almost any small (less than 50mm or so) 12V fan will run just fine. But the cold-end fan shouldn't even be controlled... it should be on all the time, wired to the +12V power supply. You *could* even run this from another 12V supply if your printer supply is too weak (but it wouldn't make a significant difference).

I think you're right that the "def" error is something else, and also explains why the fan won't run. I think you've disconnected/broken the hot-end thermistor wires. To prevent overheating, the software turns itself off if that thermistor is reading 0.

If you can look at the comms messages between printer and PC (look for a Terminal or Log window... it varies a bit depending on the software), you should learn more.

No firmware (that I know of) checks that a fan is corrected, let alone working.. The latter is possible if it uses 3 or more wires.. But most just assume its there and turn on a mosfet, this has zero feed back to the controller.

It is more likely you have damaged the thermistor cable

Un plug the thermistor cable from your controller, stick your multimeter probes into the cable plugs and measure the resistance threw the wires and the thermistor
It should be around 100K at 25C (if its anything like normal)

Thanks for the wisdom. I'll inspect the hot end and thermistor when I get home and update this topic if I resolve the issue.

There are two ports on my board for Fan1 and Fan2 and both fans were wired into a "plug" that fits the fan ports. That would make me believe it should be wired to the board.If its not running ill just put it on the supply