2011 Imac 21.5 fan speed issue

[Herb stock]

Hi, i have a mid 2011 imac 21.5 inch. A while ago i decided to do a variety of upgrades to this computer and i installed open core to use modern macos. Everything seemed to be fine until it wasn't. I started facing a high fan speed issue. Originally i thought it was the hdd because i had swapped it out but i found out after that fact that my soldered bypass for the sensor had been successful and it was actually the cpu that was causing issues.

Now my cpu fan runs at a reported 4400 rpm. For the record i upgraded my cpu from an i5-2400s to an i7-2600s. I dont know if this upgrade would cause this issue but I've exhausted most of the other known issues with these old imacs. If you know what cause be wrong with this imac.please let me know

 

[Bigwaff]

What version of OCLP and what “modern macos” version?

 

[Herb stock]

What version of OCLP and what “modern macos” version?

I am using the latest version of open core as far as i know and its on macos monterey. I would have to power on the machine again to check the exact versions though.

 

[Bigwaff]

Determine the OCLP version and patches versions you have installed. You can always reinstall everything from scratch by rebuilding a bootable USB OCLP Monterey install media.

 

[Herb stock]

Determine the OCLP version and patches versions you have installed. You can always reinstall everything from scratch by rebuilding a bootable USB OCLP Monterey install media.

Not sure if its relevant but the fan is full speed from the moment the computer is turned on. When i hit the power button it slowly ramps up to full speed and then it doesn't stop. I dont think its related to the OS. It hits full speed before the pc finishes booting and it never changes.

I dont know how quickly open core takes over in the boot process so its a possibility that it initializes early enough that it seems unrelated but im not totally sure.

 

[DeltaMac]

You should be able to control the fan speed with software, such as Macs Fan Control, or smcFanControl

 

[Herb stock]

You should be able to control the fan speed with software, such as Macs Fan Control, or smcFanControl

I tried that. It doesn't work

 

[DeltaMac]

Which software did you try?
Of course, I completely missed that you said only the CPU fan runs at high speed. The other fans are OK, so the hard drive fan is not affected by the replaced SSD (which, in any event, would not affect the CPU fan) Correct?

I do suggest that you try the smcFanControl software again, as it's what I use the most. I do know that it sometimes won't control fans, until you specifically add a favorite for the fans to the app's preferences. You should be able to add a favorite just for the CPU fan, and I would suggest adding both a low speed and a high speed favorite. After adding the favorites, then restart your iMac, and check the smcFanControl a final time, just to see if the fan comes under control when you choose the favorite in Preferences.

 

[Herb stock]

I tried both of the software you listed above. Smc fan control did not work for me and i found the software to be somewhat unintuitive.

How do i do the favoriting and such? Do you mind uploading a screenshot?

 

[Bigwaff]

Could be the CMOS battery. Unfortunately, you’ll have to take the iMac apart again to replace.

 

[DeltaMac]

Set up favorites in smcFanControl preferences.
everything about smc... is in the menubar. Just click on its position in the menubar to drop a menu. That's where you can quit the app, for example. Click on Preferences in that same menu. Click on the (+) in the top right corner of the preferences window to add a favorite. Slide the fan speed sliders to a speed of your choice. Then, click the Save button.
I use favorites to have fans running a full speed, 1/2 speed, and idle. When you have set up those Favorites, you can simply choose whichever fav you want. Nice to use on my older Mac (2008 iMac), which often heats up (ready for a re-paste of CPU heatsink, but I'm not ready to do that. So, I leave the fans running at about 1/2 speed most of the time)

 

[LangdonS]

I tried that. It doesn't work

I reccommend macs fan control `brew install --cask macs-fan-control`

 

[LangdonS]

Make sure you only have ONE fan control app at a time.
Perform an SMC reset:
Turn off imac
Wait a bit(Not really necessary but whatever)
Unplug
Wait around 15 secs
Plug in
Wait around 5 secs
Turn on

Perhaps try a PRAM reset:
Shut down iMac
Trun on iMac
press Command-Option-P-R ASAP
Release after second start chime*

*Ah.. The good ol' mac startup sound.