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iMac Overheats & Fans Won't Speed up to Cool

I have a 2007 iMac that for some reason the fans won't speed up above idle and so if it's put to heavy use eventually it will overheat and shutdown. It was a while before I had installed software that measured temperatures of devices or fan speeds inside the iMac and then determine what was happening and that indeed the iMac would shut off when the power supply got too hot.

Then I found some of these apps that let you control the fan speed manually or customize the threshold and with some of these I was able to speed the fans up. The one I chose as the best was Derman's version of Fan Control, a control panel which is automatic and effectively keeps all the temperatures normal and has been my solution to the problem. Many people seem to like SmcFanControl for some reason but I don't because it's crude and totally manual in setting the base fan speed which keeps the fan running higher than normal all the time but doesn't help much to cool if the iMac gets really hot unless you manually speed up the fan more.

The whole thing baffles me. Why can this control panel speed up and control the fans just fine and effectively cool the iMac but left to it's default control it does nothing and allows the iMac to overheat? And has anyone had this problem and found a way to fix it?

iMac (20-inch Mid 2007), OS X Mountain Lion (10.8.1), 4GB RAM, 1TB HD,

Posted on Sep 22, 2012 7:46 PM

24 replies

Mar 20, 2013 5:54 PM in response to shawnhoefer

Yes I searched out a great solution last fall that's been perfect. It's a fan control panel that adjusts the fans as needed and my iMac stays cool and quiet all the time even if I run BOINC which will max out the CPU.

Here's the link: http://www.derman.com/iMac-Fan-Control

I have the L temp set at 45 and the U temp set to 80.

Mar 20, 2013 6:00 PM in response to MagnusVonMagnum

Yes SMC Fan Control is horrible. It's great if you want to use your Mac to filter the dust out of the air. =-p That Derman Fan Control is the best I've found too and I have it on my MacBook Pro just to run it a little cooler and on my iMac which won't auto control it's fans for some reason.

Mar 21, 2013 3:20 AM in response to Razorbeam Grrl

I can't seem to get the imac-fan-control to work or even start on my imac... it lets me go through the entire install process, but after it completes I can not find the program anywhere on my system...??? I'm running 10.7.5, is anyone else using this on 10.7.5? I'm not sure where the program is going after install, I've searched my applications and even searched the imacHD and am not finding it...???

Mar 21, 2013 3:40 AM in response to shawnhoefer

OK, got it to work, but its not reading CPU or GPU Heatsink temperatures and I don't seem to be able to make the HDD fan speed up...??? Any suggestions ???

Mar 22, 2013 7:47 AM in response to shawnhoefer

Wondering if someone can point me in the right direction on an issue... I have iMac Fan Control installed and working - kind of... the CPU and GPU temperatures both show 32 degrees farenheit... The CPU temperature read fine with SMC, I'm thinking the program is not set to the right sensor, but I need a little guidance as to where to start in getting the readout to pickup the correct sensor...???

Any advice/guidance would be greatly appreciated.

Thank you.

DJTEMPO

Level 1

11 points

Jun 21, 2013 10:02 PM in response to Razorbeam Grrl

Old thread here, but I'll chime in as I just went through this over the past hour...

I have a 1st gen MacBook Pro 15".

It's been running so hot since I got it a few weeks ago, that I can't have it on my lap. Figured this was an impractical way to work, and probably not good for the computer either.

I installed "Fan Control 1.2". Just a control panel I DL'd off the web.

Set all the values such that they would provide maximum protection, and this thing is now running as cool as a cucumber. Well, as cool as a cucumber sitting out at room temperature.

If I put my ear up to the bottom/back of the machine, I can hear the fan. But with it turned around and sitting on the table as normal, I don't hear it.

Problem solved.

Chip