My iMac mid 2011 started heating up about a year ago to the point that the hard drive broke and had to be replaced.

I managed to replace the hard drive and I also replaced the power supply module as I had suspected this was the problem. I then reinstalled the correct operating system with no problem however I noticed it started heating up again.

I then got an application which showed the heat sensors and the rpm of the fans and noticed that one of the fans, the CPU fan, was saying 0 rpm. I took my iMac apart and checked the the connections of the cpu fan with a multi meter and noticed that when one of the connections was in contact with the heat sink it started to work again.

I assume that this connection is ground and had become disconnected to the PCB and so because the heat sink is grounded this makes the fan work when in contact. I then soldered this connection and the fan works fine ever since.

After all this, fixing the fan has made the temperature cooler than what is was before but it is still hot. The Secondary T2 heat sink reaches 66 degrees after about half an hour of usage and the upper left side of the iMac gets very hot to touch. From looking at the stats application it looks as though it is the AC/DC power module which heats up because the 'T2 AC/DC Sec heat sink' and the power supply temperature sensors get to around 60 degrees which is not normal and all the other temperature sensors are normal temperatures.

I have no idea how to fix this so any help would be appreciated.

1 Answer 1


This is not a problem. I have a 2010 iMac with an HDD and I have Temperature Gauge 4.1. It reports the temperature at 14 different locations in my iMac. My computer is basically idling right now. 9 of the 14 locations have a temperature that is over 60°C, with the Power Supply Heatsink reporting 75°C. The locations that are not reporting temperatures over 60°C are at 55-59°C. So 60°C is not a problem. The Average CPU temperature on my machine is reported as 59°C. One fan is maxed out and another almost maxed out. This is normal for my older iMac. The left side of my iMac also gets very hot to the touch.

  • Is it normal for them to heat up as they get older then? Commented Jul 31, 2020 at 22:02
  • i wouldn't think so. i don't know what the temperatures were many years ago but my app remembers the highest temperature for each location. I am not near these temperatures except at a few locations. So my machine has been much hotter at some point.
    – Natsfan
    Commented Jul 31, 2020 at 22:05
  • It’s just I can’t remember ever having to have the fans on full after using it for half an hour when it’s not even under any load Commented Jul 31, 2020 at 22:06
  • my CPU fan often maxes out even when doing little. I seldom turn my machine off so it has been running most of the past 10 years!
    – Natsfan
    Commented Jul 31, 2020 at 22:08
  • Yes I rarely turn my iMac off too maybe this could decrease the lifespan of the power module Commented Jul 31, 2020 at 22:11

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