Model A1224 / Mid 2007 and Early 2008 / 2, 2.4, or 2.66 GHz Core 2 Duo processor

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Why is my CPU fan running full speed?

I bought a used iMac and the CPU fan is on full speed, all the time. As soon as the computer boot chime is heard it starts up and stays running full speed. Using guides here I took the computer apart and discovered it is missing the LCD temp sensor and cable. Would this cause the full speed CPU fan, or is there a good chance there may be additional problems with the logic board even if I replace the missing sensor?

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The missing sensor would certainly cause the fan to run at full speed. If the computer seems to run fine besides the fan, there is no reason to suspect the logic board. The main question would be way the sensor is missing in the first place. I'd ask the original owner about it.

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Here's the guide for replacing the ambient sensor which may help: iMac Intel 20" EMC 2133 and 2210 Ambient Temperature Sensor Replacement


Thanks for the response. I ordered a used sensor and sensor cable. Hopefully that solves it. The computer works perfect other than this issue, I am actually using it to post this comment.

The guy who sold it too me bought it from iFixiMac who sells iMacs on eBay. Based on the conversations I have had with the guy I bought it from, I am certain he never took it apart or had anything to do with the issues with it. I am pretty confident iFixiMacs took it apart and likely took the part to fix another less scratched up iMac. What also is concerning is iFixiMacs then sold it via craigslist, not eBay, a method with no buyer security, further reinforcing the idea they just wanted it off their hands.


Consider getting a SquareTrade warranty on it. I've had good experiences on the two claims I have filed with them.


I bought a used LCD temp sensor and cable for $15. Installed them today and the computer now works 100%. Thanks for the info and confidence to fix this.


Glad I could help.


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