2011 27" iMac SSD upgrade + fan speed - Whats the current consensus?

[cyberstudio]

A couple of corrections:

• I swapped in a 75k resistor and the fan is still at its lowest speed, from that I surmise it is not anything like a thermistor whose resistance is measured. Short of paying for a commercial solution, I would say all DIY methods in the folklore appear to work only because they disable fan control altogether by shorting to ground, without the inventors themselves realizing what makes it "work". As a result, I have decided to leave the HDD temperature sensor open circuit as a safety feature so that if the fan control software ever crashes or malfunctions it will turn up the fan slowly until it reaches full speed so that the HDD is protected from overheating.
• The Platform Controller Hub Die appears to be really the platform controller hub die. The HDD temperature reading is not advertised in Macs Fan Control.

I dismantled each fan to do some deep cleaning but they were not that dusty even after 10 years. I doubt if cleaning alone would have lowered temperature by more than a degree or 2. However, I found a way to cut around 5 degrees C off my hard drive temperature. First, we observe that while the air flow is generally from bottom to top, there is an exception. The hard drive fan has its own intake vent.



The HDD fan blows both directly through hitting the main board and upwards. This is the reason for the HDD's high temperature. When the CPU gets hot the hard drive's temperature goes up, too. I am surprised the original HDD has lived for 10 years before failing in such a hot environment.



Now, I used foil tape to cover the front vent so that the incoming air can only go upwards.



I actually did that for all 3 fans. However, there is little need to seal up the CPU fan because it fits very snuggly against the housing with little room to leak air. If you do decide to seal it, however, you may need dryer-grade foil tape for that because the CPU is the hottest part of the computer.

 

[The_Croupier]

My 2010 27" iMac has a 3rd SATA port.
I left my apple 1TB drive and hooked my 500GB SSD up to the spare SATA port, I installed the SSD under my optical drive which i find useful to keep. By keeping the original apple HDD i have 1TB for storage and no fan speed issues. Obviously i installed oSX on the SSD 👍

My 2010 27" i7, 1024 original gpu with SSD boots up in 16 seconds. I'm so happy with it, but will be doing the wifi card update for handoff band airdrop later and may do a GPU upgrade to get to Catalina but think ill wait till the original 10 yr old card fails ))