Chosen Solution
Hello all, our normally good working iMac 27” 5K from End 2015 has a defects since some weeks. The Fan turns up and the performance drops down, so it is not possible to work on the machine. I tried to install the newest macOS, restart with D = no errors. TG Pro displayed that the Sensor “Power Supply Secondary Heatsink” = N/A and the fan is turning up high.
Do you have any idea how i can fix this problem? Thanks so much! Sören
Well it looks like either the power supply its self has failed or the data cable connection between the PS and the logic board has a problem. iMac Intel 27" Retina 5K Display Power Supply Replacement Jump down to Step 35 for the cable, disconnect it and re-install see if its just loose or reseating fixes things. If not I would replace both.
