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Model A1311 / Mid 2011 / 2.5 & 2.7 GHz Core i5 or 2.8 GHz Core i7 Processor

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Loud fan, hot top left edge

I have an iMac 21.5" from mid 2011 that I don't quite know what to do with.

On startup, and initial boot, it's fine. After a while though, a loud fan-like noise occurs. Given enough time, the top-left of the iMac near the ventilation strip gets hot to the touch. It seems to be coming from close to the top of the iMac, so I thought it was the hard drive. I replaced it, thinking that might be the solution. (it wasn't but it can now run MacOS Sierra reasonably well, so I'm pleased with that)

I took a closer look, hoping to diagnose it further. I installed iStat on the iMac, and it showed that all internal temperatures were hovering between 97-148 degreed Fahrenheit. At this point, the fan(s) was (were) running quite loudly.

I poked around a bit on the interwebs, and came up with two possible solutions:

-Add a Digital Thermal Sensor

-Replace the CPU fan

Just looking for some feedback as to which course of action might be preferable. If more info is needed, let me know.

Thanks in advance.

Answered! View the answer I have this problem too

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Did you or anyone change the hard drive? If so, you diagnosed correctly and you need that thermal sensor from OWC.

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It's a computer from the organisation I work at. I just replaced the hard drive today, but I see signs of it having been opened before. (this is my first month here) So my predecessor may have done some work as well.


@gryczewski - Alek - You should see this on the drives SATA cable: OWC In-line Digital Thermal Sensor for iMac 2011 Hard Drive Upgrade if you put in a non-Apple HD in.


So that part should be on there already?-- EDIT: Misread you, nevermind, thanks for the help :D


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Alek Gryczewski will be eternally grateful.
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