Model A1225 / Early 2009 / 2.66, 2.93, or 3.06 GHz Core 2 Duo processor

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High speed CPU fan after replacing optical drive with SSD

I replaced my optical drive with an SSD. I followed the guide, and all seemed to go well. I moved the temperature sensor onto the new drive.

However, a fan (pretty sure it's the CPU fan) runs on high from startup. I've tried the various fan control software to slow it down (iStat Menu, smcFanControl). They make no difference. TechTool Pro passes all tests. When I test the HDD or ODD fan, I hear another fan rev up, while testing the CPU fan modifies the now normal jet engine fan. It seems to be running at 3600 rpm.

I reopened the iMac and couldn't find anything lose. I don't see any unusual temps. Any ideas on what I've done?

Ambient Light Reading 0 lx

CPU 0 Core 7.03 A

DC-In 12V S0 3.60 A

DC-In 12V S5 1.45 A

GPU 0 (MXM) Current 1.26 A

Northbridge Rail 0 0.00 A

Northbridge Rail 1 0.00 A

CPU 0 Core 1.09 V

DC-In 12V S0 12.08 V

DC-In 12V S5 12.10 V

GPU 0 (MXM) Core 12.02 V

Northbridge Rail 0 0.00 V

Northbridge Rail 1 0.00 V

CPU 0 Core Power 7.66 W

DC-In Rail 0 43.44 W

DC-In 12V S5 17.53 W

DC-In Total Rail 60.97 W

AC/DC Output Power 141.06 W

GPU Rail 0 15.09 W

Northbridge Total Rail 0.00 W

Zone 0 Average Target Power 22.88 W

Zone 0 Average Power 22.75 W

System Ambient Air Temperature 22.12 °C, 71.82 °F

CPU 0 Die Analog 37.25 °C, 99.05 °F

CPU 0 Heatsink 34.50 °C, 94.10 °F

CPU 0 Proximity 41.00 °C, 105.80 °F

GPU 0 Die 45.50 °C, 113.90 °F

GPU 0 Heatsink 45.00 °C, 113.00 °F

Hard Disk Proximity 45.88 °C, 114.58 °F

Northbridge Die 65.20 °C, 149.36 °F

Northbridge Heatsink 60.88 °C, 141.58 °F

Northbridge Proximity 47.38 °C, 117.28 °F

Optical Drive Proximity 36.25 °C, 97.25 °F

Main Logic Board Proximity 39.75 °C, 103.55 °F

Power Supply Proximity 46.74 °C, 116.13 °F

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The higher Northbridge chip & sink temp is a clue here. What does Activity Monitor show for processes?


Nothing very interesting. The fan kicks on as soon as I hit the power button, so I don't think it's an OS X process. Something at a lower level is going on.

Here's some recent numbers. Still some heat going on.

Northbridge Rail 0 0.00 A

Northbridge Rail 1 0.00 A

GPU 0 (MXM) Core 12.04 V

Northbridge Rail 0 0.00 V

Northbridge Rail 1 0.00 V

CPU 0 Core Power 3.58 W

AC/DC Output Power 134.61 W

GPU Rail 0 14.69 W

Northbridge Total Rail 0.00 W

System Ambient Air Temperature 19.62 °C, 67.32 °F

CPU 0 Die Analog 30.50 °C, 86.90 °F

CPU 0 Heatsink 29.25 °C, 84.65 °F

CPU 0 Proximity 35.00 °C, 95.00 °F

GPU 0 Die 40.00 °C, 104.00 °F

GPU 0 Heatsink 39.25 °C, 102.65 °F

Hard Disk Proximity 38.25 °C, 100.85 °F

Northbridge Die 59.20 °C, 138.56 °F

Northbridge Heatsink 54.75 °C, 130.55 °F

Northbridge Proximity 41.38 °C, 106.48 °F

Optical Drive Proximity 29.62 °C, 85.32 °F

Main Logic Board Proximity 32.25 °C, 90.05 °F

Power Supply Proximity 41.43 °C, 106.57 °F


This sounds like an issue know to the 2010 iMac. Please check your machine identification.


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1 Answer

Chosen Solution

Figured it out with some Google fu!

iMac Intel 20" EMC 2133 and 2210 Ambient Temperature Sensor Replacement

Turns out I'd missed reconnecting the LCD temperature sensor. Must admit it's pretty lame that TechTool Pro 8 didn't flag that. Running now, I see the addition of

LCD Proximity 29.05 °C, 84.29 °F

in the sensor list. Perhaps it's important when a vital sensor doesn't show up in the list? Worth mentioning, perhaps?

Anyway, user error by not reversing step 9 b on the iFixit guide:

Installing iMac Intel 24" EMC 2267 Dual Drive or

iMac Intel 24" EMC 2267 Optical Drive Replacement

Thanks all for the help!

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bryan walls will be eternally grateful.
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