Fan Noise After Adding SSD To Mid-2011 27" iMac

[Piyono]

I posted this earlier today on the MacRumors forum.
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This morning I followed OWC's tutorial video and installed an old Samsung EVO850 SATA 500GB SSD into a mid-2011 27" iMac i5.

I used a generic Chinese SATA cable from eBay, with no in-line or other kind of thermal sensor because I was led to believe that leaving the original HDD connected (which I did) would negate any thermal sensor issues.

Yet when I powered up the machine, as soon as Mac OS (10.13.6) booted, the fans spun up to 100% and stayed there. I'm fairly certain that I reconnected all the cables I disconnected during disassembly but I'll crack it open again and double-check my work as soon as I can.

Presuming that there's no issue with the cabling, can anyone advise me on a course of action? I need to get these fans to spin down.
I'm game for any solution that results in a quiet machine that maintains safe temperatures. Pin-shorting. Software fan controller. It's all good.

Halp.

p.s. Mac OS sees the new drive so I'm fairly certain the cable works otherwise.

 

[Piyono]

For the record, my intention is to use the SSD for the OS and apps, while retaining the HDD for storage / fan noise mitigation.

 

[Chewy509]

There are a few 3rd party fan control implementations for macOS. Just need to try a few to see which one works for you...

FYI. having fans go at 100% was a common issue for a lot of older mac's when the drives were replaced. IIRC the EFI firmware only compares the new drive details against a whitelist of drives, and if the new drive is not on the whitelist, then you get 100% fan speeds. (Same with TRIM support, whilst the ATA controller in the chipset and in the drive may support TRIM, TRIM only gets enabled if the firmware and macOS agree to do so).

https://www.macupdate.com/app/mac/47386/macs-fan-control

https://www.macupdate.com/app/mac/23049/smcfancontrol

Macs Fan Control - control fans on Apple computers, also on Windows via Boot Camp

Control fans on Apple computers, also on Windows via Boot Camp. Monitoring of fan speed and temperature sensors. Solve fan noise and overheating problems, iMac HDD replacement

crystalidea.com

 

[Piyono]

Yeah, I remember that 100% fan thing from a decade ago. It was pretty hilar back then as a non-Mac-PC user.

This is the first I've heard of an embedded whitelist, however. I had always heard that it was the presence of a thermal sensor that made the difference.
I downloaded an app called Macs Fan Control—which I see you listed—and it works a charm. Incidentally the temperature report reveals that all the bits and bobs are at nominal temps. No dead sensors or erratic readings. This helps corroborate the whitelist theory.

I only wish it could be installed as the MacOS equivalent of a service, and not just in the Login Items, because the fans kick in as soon as the OS boots, before a user has logged in.