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Do late-2015 27" 5K iMacs have an AC/DC T2 secondary heatsink thermal sensor?

Since yesterday, on my iMac (A1419 EMC 2806) the fan is maxing out from power up, regardless of safe mode, recovery mode, or booting into Windows (via Boot Camp), diagnostics return PFM006 (SMC error) Assuming a thermal sensor defect, I installed iStats to check the thermal sensors. Readout below in the screenshot - all temperatures are within normal ranges, the fan is at maximum and also won't slow down if I try to do that manually, and the only temperature that's missing is the one from the power supply unit (AC/DC T2 secondary heat sink). So my question is: Is there even such a sensor in that model, do I expect a readout here? Have I thus found the probable cause and should be looking into the connection or the sensor itself? (No other hardware or software changes made recently)

Posted on Oct 14, 2021 11:56 AM

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Question marked as Top-ranking reply

Posted on Oct 14, 2021 1:54 PM

If the SMC reset doesn't help try the following: boot into Safe Mode according to Start up your Mac in safe mode - Apple Support and test to see if the problem persists. Reboot normally and test again.


NOTE: Safe Mode boot can take up to 3 - 5 minutes as it's doing the following; 

• Verifies your startup disk and attempts to repair directory issues, if needed

• Loads only required kernel extensions (prevents 3rd party kernel/extensions from loading)

• Prevents Startup Items and Login Items from opening automatically

• Disables user-installed fonts 

• Deletes font caches, kernel cache, and other system cache files


Similar questions

2 replies
Question marked as Top-ranking reply

Oct 14, 2021 1:54 PM in response to bensteele68

If the SMC reset doesn't help try the following: boot into Safe Mode according to Start up your Mac in safe mode - Apple Support and test to see if the problem persists. Reboot normally and test again.


NOTE: Safe Mode boot can take up to 3 - 5 minutes as it's doing the following; 

• Verifies your startup disk and attempts to repair directory issues, if needed

• Loads only required kernel extensions (prevents 3rd party kernel/extensions from loading)

• Prevents Startup Items and Login Items from opening automatically

• Disables user-installed fonts 

• Deletes font caches, kernel cache, and other system cache files


Do late-2015 27" 5K iMacs have an AC/DC T2 secondary heatsink thermal sensor?

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