Overheating iMac

[DavidT]

Hi

On a dual-monitor set-up (iMac), the second monitor was blanking out after some hours' use, then switching back on, only to go off after a few minutes, repeating this behaviour constantly.

I eventually figured out it was a heat-related issue. Coincidentally, I have always thought that this iMac has been extremely quiet; now I can hear the fans working and the issue has gone away after two days of using the fan control software.

I'll try to add a screenshot so you can see if any recommendations from you are necessary.

[Steven]

Hi, David.

1. You shoudn't set fans speed in relation to Ambient. This is not correct
2. Your current sensors are ok, there's no overheating. 129 C for CPU Diode and CPU Proximity values are currently wrong for your iMac. This is a known issue, we'll fix it soon

I eventually figured out it was a heat-related issue

Reset all fans to automatic control, do some extensive work on your iMac for a couple of hours, and then attach here your screenshot.

Thanks

[DavidT]

Hi Steven

Thanks for responding.

The system defaults don't seem to be working very well. I can see the temperature of the iMac creeping up but the fan speeds remaining static until it reaches 26°C.

The problem was, once the Mac goes above a certain temperature, my second screen goes awol. What happens is, the iMac screen goes blue, the second screen goes black, then the iMac screen comes back with all the windows from both screens (in other words, it doesn't know there's a second screen attached).

The second screen comes back after about 7 or 8 minutes. Then it all happens again after a similar amount of time. Most annoying.

Setting MFC to control the temperature prevents the screen blackout I'm having. I also have had problems with USB devices not being recognised and this may have the the cause.

Question: if I shouldn't set fan speeds to ambient, why is that option included?

Here's a screen shot just after the problem kicked in:

Screen Shot 2013-04-24 at 11.39.09.jpg (81.05 KiB) Viewed 10910 times

[Steven]

Question: if I shouldn't set fan speeds to ambient, why is that option included?

You could set some fan to spin in relation to Ambient, but note all of the fans.

Can you notice which of temperature sensors is too hot when display becomes black/blue/etc?

The last picture looks ok, fans normally start to spin up from MIN value when temperature is above some level. This value is unique for each mac model.

The only thing I notice here is that T of ST31000528AS, 52 is a bit much for 3.5 seagate HDD, I'd recommend setting HDD fan speed in relation to temperature from the drive. This should make the life of HDD longer

[DavidT]

Hi there

Thanks for your advice so far. Since installing MFC, I have been able to avoid the problem I described above.

Does this now look a little better to you?

[Steven]

Looks almost fine.

I'd not set so much RPM for hdd fan, 2000-2500 RPM seems to be enough (I have a similar HDD, set 43 as starting increasing temp and 53 as max value)

If you think that setting custom rule for CPU fan solves your overheating problem, I'm glad to hear that

[tone56]

hi there
I have an iMac11,1 with an Intel Core i5 27" and I noticed that the temp gauge on the magician bar is red on both the CPU and GPU most of the time so I installed Macs fan control in the hope of preventing any damage due to over heating. As a non tech user I am not sure of what the safe and normal operating temperatures should be and I have tried in vain to find a temperature guide in the apple web site . The temperature of my house during the day in summer can be between 35 and 42 degrees C so I am concerned about my Mac and have avoided using it during the hot spells. the screen shot was taken during the early morning before it gets too hot. any advice would be greatly appreciated

thanks