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

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Logic board is not powering the cpu fan

Hello! The CPU Fan on my iMac EMC 2308 Late 2009 21.5 stopped working, I replaced the fan with another one and still the new fan doesn't work.

I imagine that the logic board is not supplying power to the connector, so is there something alternative for me to power the fan?

Because without turning the cpu it heats up, I adapted another fan connected to the SATA power port, but I can't control the speed, I had to leave it at just 3.3v, which is enough to use the iMac, but it still gets a little hotter than before.

Update (12/06/23)

I put the photos attached so you understand, the logic board is not powering the cpu fan.

I also tried to power the cpu fan using the molex or sata connector to supply 12v, but that didn't work either, I tried with two original cpu fans and the logic board doesn't power it.

So I dismantled one of the cpus fans and adapted a generic fan and connected it to the sata connector, but with 12v it makes a lot of noise, so I connected it to 3.3v

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I mentioned above that if I could add the variable resistor inside the iMac and that by removing the glass I could control it, maybe that would solve it, just so I can adjust it at a speed that improves the air flow but doesn't make so much noise.


@ramonferre18311 sounds like you got this under control now. You know you can do it. You got this!!!!


@oldturkey03 - it wasn’t for you, it was to support what you had suggested.


@oldturkey03 I think I'll find a way to stay above the LCD, so it doesn't stick out of the case and look ugly.


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Let’s get a better view of things, download this great App TG Pro post a screen shot of the main window here so we can see things (alter its size so all of the sensors are visible in the one capture or take two making sure to slide the slide down to get the bottom ones.

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@ramonferre18311 - I understood your alteration, what I as looking for is the other fans and there state.

It appears the other fans are also not working! This looks like a power rail issue the fans use. You’ll need to access the schematics and board view drawings and check the voltages on the logic board.


@danj I forgot to mention that it suffered a short in the GPU Fan region, which is why it stopped working, but before in fact the CPU Fan didn't work nor the HDD Fan, but the GPU Fan worked.Even when CPU FAN had stopped, first HDD Fan stopped, then CPU FAN.

Finally, the GPU Fan stopped, but it was due to my error.

I believe that changing components on the logic board is not a viable option for me, isn't there a way to increase the speed of the CPU Fan just a little through the SATA power connector, but not make it so fast that it makes noise?


@ramonferre18311 - Sorry, without engineering a tachometer feedback circuit to put between the fan and the power source. I truly think fixing the logic board is the better and quicker way.

It sounds like you managed to short out some of the logic burning some components.

Where are you located? Country and nearest city maybe we can aim you to someone who can help you.


I'm in Brazil, more precisely in a city called Lauro de Freitas, in the state of Bahia. I think that repairing the board would not be an option because I do not have the knowledge or equipment to replace possible capacitors, resistors or any other electronic component. I also thought about buying another logic board but I also canceled the idea. If I could place the variable resistor in a way that just by removing the glass from the iMac I could adjust it, that would be great. If it was Bluetooth, even better. 😂😂


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Ramon Ferreira will be eternally grateful.
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