SOLVED: I replaced the leads coming from the fan motor and it is working just fine. Thanks for the input. If anyone else has this model, I would suggest printing and installing a wire clip in order to prevent the issue. Here is the one that I am using now: http://www.thingiverse.com/thing:620627
I am running a Printrbot Simple Metal with a heated bed and have not been able to get my fan to run recently. The fan used to run just fine (for the past 3 months in fact--since purchase). I cannot be certain, but this may be related to the cord getting snagged by the hot-end last week (cables have begun to sag over time). Nothing melted or damaged except for the hard-plastic coil used to bundle all cables together, and that appears to just be minor, cosmetic damage.
I have checked Cura settings, ensuring that fan operation is selected (starting at 0.6 mm) and that it is being told to run at 100%.
I have also sent 'M106 S255' from Proterface UI (this, from what I have researched, should turn the fan on at 100%). This command had no results.
The firmware is stock (Marlin), all exposed cables seem intact and without damage, and the plug to the control board seems to be fine. Maybe I could apply current to it directly and see if it runs?
EDIT1: I put 2 6V lantern batteries in series (voltmeter shows 12.3V) and hooked it to the fan cable; the fan did not budge (even with encouragement in the form of a slight push from the hand). Is there a particular spot in the cable that is vulnerable to failing if pulled on?
Any thoughts, suggestions, or things to look into?
EDIT2: I have disassembled the cable bundle leading to the fan and hot-end. I have found a connection point where the fan plugs into an extension cable which goes to the control board. I have applied current here and the fan doesn't move. I tested the current on another 12V fan laying around and that fan runs just fine. So, it seems that the fan has gone bad...somehow. I am still quite confused on how this would happen. Is it possible for a DC fan to "overheat" due to poor airflow? I have a shroud on the fan (http://d17kynu4zpq5hy.cloudfront.net/igi/printrbot/CnoDPS5D1CZ5EgBR.standard) and there has always been a little back pressure pushing wind out of the back of the fan.
EDIT3: So I have resorted to tearing into the fan and have applied 12V to the wires which are soldered directly to the fan and the fan doesn't work. I then applied the current directly to the solder points and the fan runs. Is there a reason why a set of wires, which look perfectly fine from the outside, would fail to run the fan?