Solved Extruder stops feeding partway into print (repeatably)

I have an interesting issue that I think I know how to solve, but I could use a second opinion. I've got a newer Robo3D R1 with the hexagonal metal hot end.

Some background: A few weeks ago, it clogged really really badly. It took me until yesterday to get around to fixing it, which I did by removing the hot end from the extruder assembly, jamming a red-hot safety pin into the top of the hot end, and yanking out a ~2 inch long chunk of mostly PLA that got stuck in there. Having solved that problem finally, I put it back together and started printing a large ABS part.

Printing went well about 30-40 minutes into a large part. It starts as a circle that is like 6 inches in diameter, so two layers of a grid bed had printed and the printer was creating the first real layer of the part. At a certain point in the print, the extruder stopped feeding. It seemed to be around a point where the extruder motor was (attemping to) very slowly feeding material over time. Removing the filament showed a small kink a few inches from the end, indicating it was having trouble being fed and the bolt was just chopping away at the filament instead of pushing it. When I pushed the filament down by hand with the end still heated, I could force out a bit of material (enough to prevent a clog from forming).

I took out the bolt and cleaned it as well as moving a washer such that the hobbing was located closer to the feed hole (I believed this was the issue at first), then tried the same G-Code again. The print ran successfully until nearly the same exact part of the print. I have both failures and it's seriously within 30 seconds of each other. The failure was identical.

What I suspect is happening is that the smaller fan that is mounted to the hot end is not spinning. I haven't seen it run in the past two days, and I believe this fan cools the portion of the hot end farthest from the tip. Since this isn't working, my suspicion is that this part is getting hot enough to soften the plastic, preventing force from pushing the filament through (forming the kink and stalling). I suspect this happens at a slow part of the print because the filament has more time to soften.

So do you all think this is my issue? Are there any commands I can use to manually power the fan so I can see if this is a code issue or a hardware issue? If my smaller fan has indeed failed, where can I get a new one? Thanks for the help.

 

The hot end fan is always on with the power supply, there is no command to trigger it. They had a batch of bad ones that they've been replacing.

Submit a replacement part request: www.robo3dprinter.com/pages/replacement-part-request

 

That is indeed the fan that is not spinning which should be. Thanks for your help!