I have similar issue with my Macbook pro retina 13 2014:
despite high CPU usage, the fan spins constantly at 1300 RPM, which causes the CPU temperature raise up to 80C.
All temperature sensors seem to work fine and I can manually adjust fan speed as well as it can be changed by MFC.
Also i tried 3 different fans and the situation doesn't change.
I tried to reset SMC, pram and to reinstall the system (was cooling down CPU manually, don't ask how)
Atm i am using MacFanControl to regulate the speed of the fan, but the issue is still present and causing some discomfort, like i can't install new OS because MFC doesn't run during OS installation and i am afraid of overheating.
Despite all components look good, the system doesn't regulate the speed of the fan.
This happened after i heavily broke my macbook and tried to repair it by replacing its aluminium body, its broken screen assembly and its noisy fan (was a bit bended which caused noise).
It is interesting that after i disconnected touchpad the fan was speeding up normally when CPU temperature was raising. The downside of this was that macbook was constantly throttling , CPU usage was 300% and everything was very slow. I had the same symptoms when camera's cable was damaged.
Can anybody help me with this please?
pictures of macbook