iMac fan running

I have a 21.5-inch, Late 2013 iMac running 10.9.5 that is around 2 years old. I've been having trouble with the fan intermittently running and not stopping. It's very loud and will run for long periods if left going. I've taken it to Apple and they say nothing is wrong with it. That it is 3rd party software causing it and that they want to re-install the system. I've looked in the Activity Monitor and not much is going on when its running. Sometimes it does it when it starts up so it's not like its running hot. I've tried unplugging it, running Applejack, CCleaner, and SMC reset. I see that there was a firmware update but when I try to run it, it says it is not supported on my system. I doesn't do it all the time so it's difficult to tell when it's fixed. Any other ideas?

barbiek said:

I've tried unplugging it, running Applejack, CCleaner, and SMC reset. I see that there was a firmware update but when I try to run it, it says it is not supported on my system. I doesn't do it all the time so it's difficult to tell when it's fixed. Any other ideas?

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It all depends on what your doing on your computer. If you're doing something demanding…then the fan rpm will increase suddenly. And if you stop doing that demanding thing…then fan rpm's will decrease.

You took it to Apple…and they said nothings wrong!

And BTW…get rid of the "cleaning" apps. They can cause more trouble then they are worth. We only recommend using the maintenance app called "Onyx".

- Nick

And are you running SMC FanControl or anything similar?

I'm not running SMC Fan control. I did download it and try it as a fix, but it didn't help so I uninstalled it. As for what the computer is doing when the fan comes on, sometimes it has just started up and is doing nothing that I can tell. I pull up Activity Monitor and not much is going on. I will try Onyx next time.

Next question ~ ever had the hard replaced? Have the same model and yet to hear the fans.

No. Nothing has ever been replaced. I've been told twice now to have the fans cleaned. I wouldn't think they would be that dirty yet, but I'm willing to try anything.