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Gareth
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iMac Fan is running all the time

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Hello!

OK I purchased a mid 2011, 21.5, i5, 2.5ghz iMac from ebay the other day that was listed as slightly faulty. As I was looking to buy my first iMac and I had a tight budget I thought I'd give it a go. I work with computers and thought I could have a go at fixing the issues.

So this brings me to the problem, the seller said it was bought as part of an office clearance so not much history behind it and that when it was on one of the fans was noisy.

It's arrived today and true to form one of the fans is noisy. I've spent the past couple of hours researching the issue on the internet. First thing I did was run the online AHT. This brought back an error code of 4MOT/4/40000002:CPU-0. I think this refers to a faulty cpu fan but the noisy fan is coming from the right hand side of the screen?

I then downloaded smcfancontrol. Currently the ODD fan is running at 4300rpm and 46 degrees (I presume this is the noisy fan I hear). The HDD 1099rpm and 46 degrees and the CPU fan 0rpm and 46 degrees?

So I suppose my question is, where do I start to fix this? Why would a faulty cpu fan make the odd fan run at max?

Thanks in advance

Edited by: Gareth ( )

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machead3
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To keep you from cooking the CPU. When some of the sensors or fans fail by default mode all the fans kick into high to try to keep the user from killing the CPU by continued use of a faulty machine. Try replacing the fan AHT identified (you are correct the EFI blames the CPU fan).

If this answer is acceptable please remember to return and mark it.

Thanks for your reply. I will order a cpu fan and see if it works. I have had time to open the iMac tonight and noticed it didn't seem to spin at all. I'm not sure though if it should spin all the time, or it only spins when it gets too hot?

Gareth,

I think the fans only run in response to heat… If the GPU and HD fans are on and that one isn't I suspect it's bad. If you can remove the fan without damaging the connector you could connect it to the HD fan (one that is running) if it doesn't run then you know it's dead.

machead3,

OK, I've got the cpu fan out to test but it's connector is bigger than the other 2 fans connectors so I suppose I'll have to wait until the replacement arrives.

Gareth,

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eman05
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Check your hard drive and make sure it is an Apple branded drive, on some iMac's 2009 and above if you replace the hard drive with a non-Apple firmware model you will get this problem.

That's possible but I'm believe'n in the AHT error code.

machead3,

Just further to this, I don't think there is, I cannot see a temperature sensor cable attached to the hard drive either?

Gareth,

New fan arrived and it hasn't resolved the issue. On closer inspection there is a scorch mark next to the fan connector. I think one of the resistors has blown but I don't know if they can be replaced?

Gareth,

Can you take a hi-res picture of the area and a tighter one of the component so we can see.

Dan,

See below links to 3 pictures I have taken. I think the missing component says L5720. Would be good if someone could upload a picture of that area on a working logic board. http://i60.tinypic.com/2sbo7s3.jpg http://i59.tinypic.com/2zzuvfd.jpg http://i57.tinypic.com/4liyl2.jpg

Gareth,

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