iMac running hot, what's wrong?

Question

Trashtone Author

Level 1

4 points

iMac running hot, what's wrong?

My iMac (24" Mid -07, 2.4G Intel C2D, 4GB RAM, OSX 10.6.8) is running real hot and it's not just the summertime.

Temperature Monitor gives me following values:

Hard drive bay: 55c

Display screen proximity: 59c

CPU A heatsink: 59c

Graphics processor chip 1: 70c

Graphics processor heatsink 1: 71c

Graphics processor temperature diode: 75c

Main logic board: 62c

Optical drive: 49c

Power supply position: 89c <------ ***??

Wireless module: 69c

Activity Monitor values:

CPU % User: 26.44

CPU % System: 5.99

CPU % Idle: 70.67

Threads: 588

Processes: 78

Memory Free: 720.6MB

Wired: 410MB

Active: 2.35GB

Inactive: 564MB

Used: 3.30GB

VM Size: 153.77 GB

Page ins: 45.08 GB

Page outs: 2.53GB

Swap used: 2.73GB

I could fry an egg on the computer if I wanted. I have had to replace my hard drive twice because of temp fails and have reinstalled OSX a few times without any help. Fans running like ****. I am running Google Chrome with three windows (21 tabs in total)

I can't say the computer is reallly "unresponsive" per se, but it is slow and not something you'd expect of a 2.4G C2D machine. If I open a Youtube tab, the videos jerk like crazy.

Any suggestions??

iMac, Mac OS X (10.6.8), XServe G5, Mac Mini G4 + PB G4

Posted on Aug 20, 2012 8:04 AM

Reply

Answer 1

Best reply

RRFS

Level 5

4,522 points

Aug 20, 2012 8:07 AM in response to Trashtone

As old as your iMac is, have you cleaned out the dust? Dust buildup can lead to over heating issues. Remove any and all things plugged into it including the power cord, Remove the RAM access grille. Vacuum all openings starting with the RAM access area (air intake). Vacuum all ports and plugs, DVD slot and the opening across the top of the rear of the body. Blow compressed air through all your openings and vacuum again to remove any dust you loosend. Reinstall the RAM grille. Plug in the keyboard and mouse if not blue tooth. Insert power cord...

You are now in a perfect position to do a

SMC RESET

http://support.apple.com/kb/HT3964

Shut down the computer.
Unplug the computer's power cord and ALL peripherals.
Wait 15 seconds.
Attach the computers power cable.
Wait another 5 seconds and press the power button to turn on the computer.

It is the 5 second timing that initiates the reset.

Here is a link to a Widget to monitor your temps and other operations:

http://islayer.com/apps/istatpro/

Reply

Answer 2

Trashtone Author

Level 1

4 points

Aug 20, 2012 8:14 AM in response to RRFS

Thanks for your reply!

I have indeed opened up (the whole computer, not just the RAM grille) my iMac twice and on both times, vacuumed the computer and blown compressed air on fans and all available orifices and on both times there has been a mountain of dust inside, but the heat problems have continued after that.

I'll do a SMC reset and try if it helps, thanks!

Are there any DIY guides as to how to open or disassemble the fan intake/exhaust pipes? I might need to check that too if there is any remaining dust that didn't get blown out the water..

Reply

Answer 3

RRFS

Level 5

4,522 points

Aug 20, 2012 8:30 AM in response to Trashtone

Use iStatPro and check your fan speeds or run the Apple Hardware Test and make sure the fans are working.

Reply

Answer 4

Aug 20, 2012 8:34 AM in response to Trashtone

Hi: Use the Apple article below to determine what activity(ies) are causing your CPU to be used at 26% and you will find the problem.

http://support.apple.com/kb/TS1473

Reply

Answer 5

MichelPM

Level 10

80,980 points

Aug 20, 2012 8:38 AM in response to Trashtone

Have you tried installing and using

SMC Fan Control?

This app will let you set the rpm speeds of the iMac's internal fans manually.

Initially, this app is setup so you can't go below Apple's initial fan speed settings.

You can only increase the rpms.

I would try this

iMacs's run too hot, anyway.

I keep posting this fact, but many users ignore this.

Conputer conponents fail prematurely from the excessive heat build up inside these new design iMacs.

It's like the innards of the iMac are being slowly roasted to failure from within.

Not a good thing at all!

I use SMC Fan Control on my 2009 iMac that I purchased used 5 months, ago.

Plus, I run a small fan at the back of the iMac, also.

The increase in the fan speeds make the iMac only a little noisier and no longer completely quiet, but the tradeoff is that most of my temps inside my iMac are much cooler, now.

I do not know how the previous owner treated this iMac, but I am trying to run my iMac cooler so I can, at least, get another 4 or 5 years of troublefree/component failure free use out of this Mac.

Reply

Answer 6

Trashtone Author

Level 1

4 points

Aug 20, 2012 9:04 AM in response to MichelPM

I have tried (and use) SMC Fan Control and it helps. The machine is just very very loud because SMC-FC fires off some auxiliary fans not running by default (there is only one(?) fan audible when the machine is running hot, there might be others too but like said I can't hear them)

Shockwave Flash (Chrome Plug-In Host) and Chrome seem to be the biggest CPU hoarders. iStatPro says my fans run at these rates:

Optical drive: 699rpm

Hard Drive: 1239rpm

CPU fan: 3326rpm

Reply

Answer 7

RRFS

Level 5

4,522 points

Aug 20, 2012 9:36 AM in response to Trashtone

Using SMC can you get the other two fans up to a higher speed? I am suspect of the Optical Drive Fan, the less than 1000 rpm speed seems awfully low considering 3300 for the CPU

Reply

Answer 8

MichelPM

Level 10

80,980 points

Aug 20, 2012 9:48 AM in response to RRFS

Normal default for the OD fan on my iMac is 900 rpm.

I have it running at a new min. speed of 1250 with SMC FC.

And yes, Adobe flash is a CPU hog!!!!

If you spend a lot of time on the web watching streaming web videos, most likely they are using Flash as the video container. FLash is a real CPU, GPU hog and a drain on the entire OS X system.

It's no wonder your CPU fans are cranking to 3300-3500 rpms.

The CPU is really working when Flash content is active.

Reply

Answer 9

Trashtone Author

Level 1

4 points

Aug 20, 2012 3:21 PM in response to MichelPM

I'll have to use FlashBlock or somesuch because banners around websites are in Flash too, so it's not just youtube etc. Also if I have, say, just Lightroom open, the fans are pretty noisy. I'm guessing the mac is just so old that the 4GB (max) RAM for apps these days just isn't enough and they have to swap out and use more CPU time for that..

If I crank my fans on top speed, I get 4399rpm on the ODD, 5482rpm on the HDD and 3312rpm the CPU fan. At this point you have to have earbuds on and listen to music because it's so loud..

Do the recent imacs (2010 and later) have these sort of issues too or can you run a bunch of apps and still have a near-silent machine?

Reply

Answer 10

RRFS

Level 5

4,522 points

Aug 20, 2012 3:41 PM in response to Trashtone

It's your power supply temp that has me concerned. Since you were able to get the fans blowing pretty good I would say they are probably OK. It looks like youhave the CPU fan running at max. Try ramping the other two fans up up to 1800 and see if that helps with the temps.

Reply

Answer 11

MichelPM

Level 10

80,980 points

Aug 20, 2012 4:04 PM in response to Trashtone

You only have 4 GBs of RAM in your iMac.

Your iMac can take 6 GBs Max.

OS X, by itself, can use the entire 4 GB just for OS system use.

If you're using Adobe Lightroom, you need that extra 2 GBs of RAM to put some relief on the CPU and the HD.

You are probably getting a lot of virtual memory swapping between RAM and HD as well as a very high page in/out count.

You can buy reliable RAM from Crucial Memory or OWC.

Here's the specs on the RAM

Memory Slots 2 - 200-pin PC2-5300 (667MHz) DDR2 SO-DIMM

You can't have a lot of high CPU, RAM intense apps open and expect your iMac to stay silent running.

Not going to happen. Esspecially if your iMac doesn't have sufficient RAM

The fan setting are for minimum fan speeds to have them constantly working, but keep your iMac cooler.

You may see less CPU and page in/out VM activity if you install that extra 2 GBs of RAM

Lightroom would have more RAM resources to chew on.

Also, you may consider re adjusting your fan speeds at that point. I would drop your speeds down anyhow, in the meantime because constantly running the fans at these high rpm speeds is actually sucking in extra dust, lint and dirt into your iMac faster and heavier.

The auto fan control of the iMac is designed to ramp up on its own when the iMac's main components start heating up.

You use SMC Fan Control to set higher min. speeds so they stay always running and will ramp up to higher speeds quicker when needed.

I would set the fan speeds at somewhere between 1400-1800 RPMs staying, at the very least, under the 2000 RPM range.

You'll reduce the fan noise to a minimum, not suck in as much dust and dirt and should help to keep your iMac constantly on a cooler side.

It, also doesn't hurt to run a small fan, as I do, blowing on the back of the iMac. This will help to dissipate heat from the back of the iMac quicker.

Reply

Answer 12

Trashtone Author

Level 1

4 points

May 11, 2013 2:37 PM in response to MichelPM

Well guys..

I'm still having the same problem. I've reset the SMC several times (not the PRAM though, as by reading Apple's descriptions it doesn't help much with the airflow side of things), without any help. SMC Fan Control hasn't really helped, the computer just becomes very noisy.

Every time I boot up the mac, let it run for a minute or two, the fan speeds ramp up and the computer becomes pretty noisy so it's definitely not an issue with any applications since Finder will be the only thing running.

Either my iMac is just supposed to be this way, or one theory I've yet to test is to open up the computer, try removing any and all fans that are accessible and adding a drop of sewing machine oil onto the fan bearings, ie. if the fans are running faster than they should because the bearings are full of dirt.

My Temperature Monitor readings are still like this:

Hard drive bay: 57°C

SMART Disk: 55°C

Display screen proximity: 59°C

CPU A heatsink: 54°C

Graphics processor chip 1: 64°C

Graphics processor heatsink 1: 65°C

Graphics processor temperature diode: 70°C

Main logic board: 58°C

Optical drive: 49°C

Power supply position: 89°C

Wireless module: 63°C

What have me worried are the GPU temp diode and the PSU temps.

And what I'm really interested in is actually finding other users who have had the same problem and find out if anyone has actually tried opening and cleaning the fan innards to see if that alleviates the noise.

Thanks to all.

Reply

Answer 13

Trashtone Author

Level 1

4 points

Oct 11, 2015 11:39 AM in response to Trashtone

Over two years later, I still have the same problem. I just did a fresh OSX install and am only running Safari, and the fans are on high speed again. It's all the same whether I have one app or a dozen running. And this time round I haven't installed SMC Fan Control or iStatPro so I don't know what speed they are really running, but so much so that the computer definitely isn't silent.

What I have noticed though is that if I set the display to blank after one minute and wait for some time, the fans will spin down and I end up with a very silent computer. Once the display goes on, it doesn't take much time for the fans to rev up again - so I think this narrows it down to an issue with the display.

Anyone?

Reply