Model A1311 / Late 2009 / 3.06 or 3.33 GHz Core 2 Duo processor

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After SSD installation HDD prox. Sensor is at 249°C; Fans running high

Hey Guys,

yesterday i installed my brandnew Samsung 256GB Pro SSD into my iMac.

My problem now is am extremly high running CPU-Fan. My first guess was the usally SSD fan control fix but unfortunatly this wasnt helping me out...

My next Step was running the AHT and after testing the logic board it produced the following Error Code:

4SNS/1/C0000008: TL0p--124

(during the test the imac went silent for a couple of seconds)

In MacOS iStatMenus shows that the

Hard Drive Proximity is at 249°


LCD Proximity is at 128°

everything else is at low Temp.

So how do i fix this?

Did i miss a cable?! (extremely unlikely)

Did i broke something? (WHAAAAAAA!!!!)

Please help me.

PS: Thank you guys so much and im sorry for my english, since im a german guy. :) )

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I remember replacing the HD on an imac before. It did the same thing fans will spin at fast speed.

From what I remember the cable for the sensor plugged in from the logic board to the hard drive.

To remedy the issue, I shorted the two cables for the sensor (connect them together)

After that then it worked perfectly.


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Thank you! But i added a secondary SSD to the iMac and didnt replace the first one. So i dont think there is any other sensor cable right now.



When I replaced the HDD on my I-Mac, Intel Core i3 running at 3.06 Ghz, there was a small molex type connector on the main board, right near the hard drive, which in my teardown instructions was labelled as 'Internal Temperature Sensor'. They had cautioned me, in the instructions, on removing this connector to gain access to the HDD as the solder connection on the main PCB could crack during removal. Check the solidity of this connector because, if it is broken, it will give a false signal to the Fan Controller circuit. If it has to be re soldered, you have to gain access to the bottom of the board.

There is also a utility that you can download, called SMC FanControl, which allows you to set the cooling fan ON and Off temperature in the i-Mac. I used this utility to maintain my internal temperature to no mare than 120 Degrees Fahrenheit, as the iMac would start to get 'Flaky' at about 140 degrees.


Well, as I had used the same instructions when I took apart my i-Mac, I don't remember seeing or reading about any 'prox' sensors. If you are talking about the thermal sensors, these are the units attached to the main board, through the aforementioned cables and connectors, with the fragile 'Molex' connector we have been talking about.


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thank you for answering!

But is there any way to find out the locations for the two prox sensors on the logic board? This would be great i want to check the specific locations on the logic board.


This was my teardown instruction: Installing iMac Intel 27" EMC 2390 Dual HDD or SSD Drive

There are thermal sensors in step 20 and in Step 11 & 14.

And i dont think anyone is connected to my problem...



I did the same to my iMac. What I realized that the 2.5" harddisks generally don't get hot, especially the SSD, so I removed both the sensor connector as well as HDD Fan connector. I haven't had any problem with either so far.


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