Extruder heatsink fan not spinning

So… in my months-long on-and-off quest to fix my CS class’s TAZ 5, I think I’ve finally narrowed down the last issue: the extruder heatsink fan isn’t spinning. I believe it’s connected to the RAMBo correctly, and I have just replaced it (because I may or may not have let the magic smoke out of the last one). What are some common issues that might cause the extruder heatsink to not spin?

Those fans were pieces of junk. They frequently burned out, and replacements are spendy and still fragile. It’s almost certainly the fan itself. It’s possible it’s the harness or the board or something unplugged, but given the high fan failure rate it’s usually the fan itself. If possible, switch to a different style by printing a different carriage and whatnot in abs.