I have acquired a 2nd-hand mid-2015 MacBook Pro which I use connected to 2x cinema displays (the laptop itself has some screen damage).
When connected up for the first time I noticed it was going insanely slow (16gb 2.8ghz w/ Radeon R9 2GB) even compared to my early-2013 model with half the spec.
Checking Activity Monitor, I noticed kernal_task was using 400% of CPU (since then I have seen over 1000%). I looked up the cause and that it was overheating so opened it up and cleaned all dust out with blowers etc. to the best of my ability - no change.
I noticed using the laptop without anything plugged in seemed to be okay, so I initially thought having 2x displayport connections to screens was doing it. Since then I've discovered (like right now) I can have 2 screens plugged in and it's okay - then sometimes I add USB devices and it's okay - but when the system really starts working and needs fans - that's when things go bad.
So I installed iStat Menus and have discovered that my right fan is not operating (constantly 0rpm even when the left is 6000+ rpm).
So I'm wondering if a) this is the root cause (and not a symptom of the cause) and b) what I can do to fix.
Even though I cleaned it I did notice at the time its movement wasn't as smooth as the left - would cleaning help or would I need a replacement?
I've replaced MacBook components before so am quite confident in doing this if needed, but the fan isn't too cheap / available here so I'd like to know if I should expect further issues or what.