iMac 21,5 late 2013 - 820-3482 ambient sensor - LCD Poximity - Discs Temp issue


New member
820-3482 A

I got this machine after a client DIY disk swap attempt. The screen was damaged as well the lvds flat wich I allready replaced. Now the machine presents an issue that prevent the system to run quiet... Fan spins at full speed probably due to the sensors misrepresented temperature values which are as follows:

Ambient 19?C
Ambient 255?C
LCD Proximity 128?C
Disc 1 249?C
Disc 2 129?C

Those values reported from HWmonitor and could explain why the system sets the fan at high speed.
Consider also that I replaced the SSD with the original HDD in order to exclude the disk variable from the equation...

Could be a data line that involve those 4 sensors I don't know.

Anybody knows where to look at for this sensors issue?
Last edited:


New member
I found this note on page 50 of the schematic:

Internal sensor of the EMC 1414
will be used as the ambient sensor.

Hw Monitor reports 2 Ambient sensor values, one seems fine but I don't know where those are belonging to on the schematic.


New member
me stupid, it was on the previous broken display and didn't find it untill now ;-) Could just be this one that was missing?


New member
I was asking myself what am I missing in that 2 pins connector next to the lvds... The sensor was attached on the original screen I just received from the client and guess what? That seems to have solved the issue with the sensor of course and the fan now spins normally.

Sorry for have been so stupid...


Staff member
You're welcome!
A sensor error can block entire bus where it is connected.
That's the reason of multiple errors...