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2009 27" iMac fan slowly ramps up to full speed

Jimmy-Chivas

Jimmy-Chivas

macrumors member
Original poster
Aug 22, 2022
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I picked up a 2009 27" iMac, did a full refurb on it (complete cleaning, new thermal grease on CPU and GPU including white RAM thermal paste for GPU memory), replaced hdd with ssd and included a temp sensor. The unit works fine, but after about 20 or 30 minutes the fan will run at full speed and just stays that way.

I have had plenty of units that run at full speed right from boot up before (when there is no temp sensor, or no hard drive, no optical drive), but I haven't come across this situation before.

Perhaps something is getting really hot over 20 to 30 minutes time, which would makes sense. However, I need to find out which component that actually is.

Any recommendations on bootable diagnostic apps I could use to check temps on CPU, GPU, SSD in real time so I can diagnose this? Or perhaps there are some other things I should check as well? Thank You!
 
Jimmy-Chivas

Jimmy-Chivas

macrumors member
Original poster
Aug 22, 2022
36
17
BrianBaughn said:
I assume you mean the fan ramps up without running any apps.

What version of macOS is it running?
Click to expand...
Yes Sir, it will eventually ramp up if left in idle at the main menu of Ultimate Boot CD for example. With No OS or drive present the fans run full tilt of course, but this is normal.

It currently has Zorin OS 16.2 (based on Debian I think) installed on an ssd. I've done about 5 systems with this OS and the fans run at normal speed most of the time using the OWC temp sensors with all of them. However, this one unit seems to be an anomaly so far.
 
Jimmy-Chivas

Jimmy-Chivas

macrumors member
Original poster
Aug 22, 2022
36
17
Update: CPU and GPU fans are around 900 - 1000, temps for both seem fine, but the hdd fan is around 4200 and seems to be staying there. The system temps overall are normal, so the ssd temps should be normal. CPU temps are around 100 ~ 110F. Systems seems just fine except for this stupid hard drive fan.

I think maybe I used an OWC thermal temp sensor for a 2011 iMac, not sure if that makes a difference? I suppose I could look for a Linux app to control fan speed? Is that my only option with this unit? Just set the fan speed at around 1200 and forget it?
 
CooperBox

CooperBox

macrumors 68000
Nov 28, 2010
1,886
2,161
France - between Ricard & Absinthe......!
It sounds like you know what you're doing, but I'll ask this question anyway. What thermal paste did you apply to the CPU and GPU, especially what was the white paste applied to the GPU memory and was it applied in thick amounts? I've totally refurbished several iMacs 2009-2011 and find that the correct paste applied to the GPU VRAM chips is of great importance to prevent overheating. I always use K4 Pro and K5 Pro.
Must admit I've never installed any Linux distros on these iMacs as I've always found High Sierra runs superbly with a current version of FireFox and updated search engine.
What made you choose Zorin? Does it run better than Sierra or High Sierra?
 
Last edited:
Jimmy-Chivas

Jimmy-Chivas

macrumors member
Original poster
Aug 22, 2022
36
17
For the CPU and GPU I used Noctua NT-H1. For the GDDR modules on the graphics card I used K5 Pro. K5 is applied thicker of course. Stuff is just like cake icing. Tastes pretty similar too! 🤣

I am really impressed with Zorin OS 16.2 and how well it runs on these machines. You can even sync an Android phone and it works flawlessly.

I don't trust Apple and prefer Linux anyway. I certainly do not trust Google, so I use Android AOSP phones, which is essentially a de-Googled phone with stock Android. Which means no Google services are running on it. I prefer to host my own services instead of letting big tech harvest my data for free.

​

 
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CooperBox

CooperBox

macrumors 68000
Nov 28, 2010
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France - between Ricard & Absinthe......!
Jimmy-Chivas said:
For the CPU and GPU I used Noctua NT-H1. For the GDDR modules on the graphics card I used K5 Pro. K5 is applied thicker of course. Stuff is just like cake icing. Tastes pretty similar too! 🤣

I am really impressed with Zorin OS 16.2 and how well it runs on these machines. You can even sync an Android phone and it works flawlessly.

I don't trust Apple and prefer Linux anyway. I certainly do not trust Google, so I use Android AOSP phones, which is essentially a de-Googled phone with stock Android. Which means no Google services are running on it. I prefer to host my own services instead of letting big tech harvest my data for free.

​

Click to expand...
Interesting! I know what you mean about not trusting Apple and Google. I currently use iMacs, Macbook Pro17", PowerBooks and an early MacBook Air and can't remember the last time I used Safari or Google on any of them due to perceived 'big brother' issues.
Been using Macs since 2002 and never had a virus, so my choice of up-to-date FireFox and alternative search engines have to make sense - always liked DuckDuckGo. Now preferring Mojeek.
I can only smile when I see some websites saying that when faced with an iMac GPU issue, 'Do not put your GPU in the oven, it will cause the chip to expand resulting in a temporary fix, a few days, a week, maybe a month, but it will fail again." Generally I agree, and I'm sure this has put a lot of people off. However there's always a BUT.......!
I have performed several iMac GPU 'bakes' under very controlled conditions, then repasting using K4 Pro and K5 Pro, plus incorporating a number of internal cooling enhancements (removal of HDD and optical drive, plus SSD install etc) plus a few other tweaks, and have at least 3 early 27" iMacs which are still running well after 2 years plus. Like yourself we are saving these potentially excellent machines from the dumpsters and landfill.
 
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Jimmy-Chivas

Jimmy-Chivas

macrumors member
Original poster
Aug 22, 2022
36
17
CooperBox said:
Interesting! I know what you mean about not trusting Apple and Google. I currently use iMacs, Macbook Pro17", PowerBooks and an early MacBook Air and can't remember the last time I used Safari or Google on any of them due to perceived 'big brother' issues.
Been using Macs since 2002 and never had a virus, so my choice of up-to-date FireFox and alternative search engines have to make sense - always liked DuckDuckGo. Now preferring Mojeek.
I can only smile when I see some websites saying that when faced with an iMac GPU issue, 'Do not put your GPU in the oven, it will cause the chip to expand resulting in a temporary fix, a few days, a week, maybe a month, but it will fail again." Generally I agree, and I'm sure this has put a lot of people off. However there's always a BUT.......!
I have performed several iMac GPU 'bakes' under very controlled conditions, then repasting using K4 Pro and K5 Pro, plus incorporating a number of internal cooling enhancements (removal of HDD and optical drive, plus SSD install etc) plus a few other tweaks, and have at least 3 early 27" iMacs which are still running well after 2 years plus. Like yourself we are saving these potentially excellent machines from the dumpsters and landfill.
Click to expand...
Yes Sir. They are great machines with a lot of life left in them, and I am very grateful for this forum. It has been an incredibly useful resource for me. I have picked up 15 iMacs so far, at mostly bargain basement prices, and I have yet to have even one of them fail to power on. There are some various issues here and there, but they are definitely worth fixing. Some of them are destined to be retro-gaming machines, others are definitely daily drivers.
 
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Jimmy-Chivas

Jimmy-Chivas

macrumors member
Original poster
Aug 22, 2022
36
17
Update: Installed the appropriate hdd thermal sensor for 2009/2010 iMacs and the unit is quiet as a church mouse. HDD fan running at around 1100 RPM (idle). CPU and GPU fans running at around 1000 (idle).

Now I have a spare 2011 thermal sensor and at least three 27" 2011 units in need of inspection/refurb, so the best overall unit will get a nice SSD upgrade.

On the current 2009 unit in question, the VSync cable was completely wore out and wouldn't go back in this time, so I had to wait a few extra days for a replacement before I could test the fans. All Good Now. Maybe this unit will run for another 5 to 10 years? Who knows. It is an experiment.

Will make a decent browsing machine at least.

Thanks for your input everyone!
 
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Jimmy-Chivas

Jimmy-Chivas

macrumors member
Original poster
Aug 22, 2022
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Last edited:
EugW

EugW

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Jun 18, 2017
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Jimmy-Chivas said:
Okay, Thank You Sir. Will give that one a try for next time.

*Will this work for all 2006 - 2011 Intel iMacs? Anybody know?
Click to expand...
The optical drive temp sensor solution is specifically for the 2009-2010 iMacs AFAIK.

Actually, you don't even need any temp sensor. You can simply short the circuit. ie. Cut the hard drive temp sensor wire and then twist the ends together. That will read as 0 (or blank?), which is good enough to prevent the fans from ramping up.

I used the optical drive temp sensor method because it's a more proper solution, as it provides a real temp reading. I didn't actually install the temp sensor on the drive though. I installed it on the metal drive bracket, just in case I want to swap out the drive in the future. Putting it on the bracket means I can swap the drive in the future without removing the sensor. I figured my SSD housing was metal, and the bracket was metal too, so there would be reasonable heat transfer to the bracket (which acts as a giant heatsink), so I'm not too concerned.

IMG_3243.jpg


I don't run fan control software, but I installed it temporarily just to confirm the sensor was working. You can see in the pic that it's reading as 25 degrees Celsius.

SSD temp sensor.png
 
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Jimmy-Chivas

Jimmy-Chivas

macrumors member
Original poster
Aug 22, 2022
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@EugW I appreciate the detailed write up Sir. Looks exactly like the RPM's in mine. Now on to salvaging the next refuge iMac.
 
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