Fan control software freezes iMac 2011

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Running 10.12.6 on a 27" Mid-2011 iMac (3,4GHz i7) 16GB RAM.
I had one of the internal hard disks replaced professionally with a 1TB Crucial MX500 which I use as my boot disk
When booting from this disk initially the fans soon started to run at full speed, but I discovered SSDFanControl and installed it. Problem solved. Nice quiet Mac.
After about six months, I found the mouse and keyboard suddenly becoming unresponsive, and the spinning beachball of death appeared on an otherwise frozen screen. Sometimes this happened at boot before login, sometimes after about 5 minutes or so. The only thing to do was to turn off the computer and start it again, without restarting processes which were running at the time of the freeze. There seemed to be no rhyme or reason or pattern to this behaviour.
I eventually tracked it down (I was blaming everything from Chrome update processes to anty-virus software) to the daemon that is installed by SSDFanControl that reads the S.M.A.R.T. data from the disk, and feeds it into the fan controls. I uninstalled the app and deleted the daemon and everything was fine except for the noise. Re-installed, and it started to freeze again. Uninstalled for good.
I looked at MacsFanControl, but the same thing happens, though it takes longer to have its evil way with the computer. I am now working with a machine that is never silent after the first 10 minutes after boot, and at its worst reminds me of standing in the middle of a runway at Heathrow.
Is there any explanation and/or cure for this? I've seen an OWC cable that promises to solve the issue by faking the Apple temperature chip on the disk, but that means cracking the case again. Software solutions preferred.
 

Cory Cooper

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Hello,

Yes, it sounds like when the drive was replaced, the proper sensor wasn't installed, or possible other sensors weren't reconnected. Because of this, the fans will spin up to protect the internals. The freezing issue does sound like a thermal issue, and will probably require some form of hardware repair/adjustment to permanently correct it. The fan control applications aren't a permanent substitute for proper hardware repairs, and other internal components can be damaged if the Apple-designed cooling system of sensors/fans isn't work to spec.

It could also be a sign of something else failing, since it was working for the previous six months. I don't know of any other software fix that I would recommend.

C
 

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