27 iMac (Late 2009) optical drive/CPU fan issue after hdd replace

This sounds like the temp sensor may have been disconnected or have a poor connection.

You may need to crack open the case again and check the temp sensor for the HDD is stuck back down on the top of the drive and is connected to the motherboard.

Hope this helps

Hi Orlandosk2

I have the exact same problem as you describe. Late 2009 iMac, changed hdd and the fans are driving me nuts.

Have searched the net for a solution, but cant find a good one.

Please let me know if anyone got a solution

Hi,

I'm afraid this is unavoidable when replacing HDD in these iMac's.
The fans spin up because the iMac is unable to read the temp of the new HDD. Some say that Apple use a custom firmware in their drives. Even if you replace with an identical replacement, without Apple's firmware, the iMac won't read the temperature.

The good news is that there is a software fix:
http://www.hddfancontrol.com/

This worked perfectly for me. They have a free trial period so you can give it a shot and see if it works for you.

Hope this helps...

Orlandosk2 said:

Recently on my iMac I got a smart disk failing error and my computer would not boot up without the beach all spinning constantly to where it was unusable.


I decided since I am out of warranty to replace the hard drive myself with another 1TB seagate barracuda http://www.bestbuy.com/site/Seagate...skuId=8490625&st=Stagnate barracuda&cp=1&lp=2

The install went good and iOS lion is now on the drive. My only issue is that now the CPU and OPP fans run too fast and are loud. Hdd fan runs around 1100RPM, opp fan and CPU run around 3500-4000rpm.

I decided to put the old drive back in to see if that would fix the fan issue. Even with the old hdd they are running at the same speeds. Prior to install they werent an issue.


Any ideas how I can fix it? I've been up night and day trying to figure it out. I want to just go buy a new iMac bad, but I know a new one is coming shortly.


I reset PRAM and did the cable unplug reset as well.

Thanks in advance

Click to expand...

This is a known issue with the 2009 iMacs. The easiest fix now is to buy software that lets you manage the fan speeds. I'll let you determine which you get

I just shorted out the HDD sensor cable when I replaced the drive.

I have tried the hddfancontrol, and that is working just fine. But that is not the problem.
As you can read in the start of this thread, it is the CPU and the OPP fans that are running too fast after the hdd change.

So lets focus on those fans

Could you have not reconnected the temp sensor for the LCD screen?

revat said:

Could you have not reconnected the temp sensor for the LCD screen?

Click to expand...

Thanks ****in hell of a lot man, you saved my life. I have tried everything. It was the LCD temp sensor cable that was not connected.

Thanks again

Hi guys, I have the same exact problem, I replaced the HDD with a SSD. I knew beforehand that I coudl expect some problem with the HDD fan because of the HDD temp sensor not connected anymore, but this one is ok running at 1100 rpm, the noisy and uncontrollable fans are the Optical fan and CPU fan running around 3500 to 4000 rpm.

I am wondering which one of the 3 cables you need to disconnect to take out the lcd , is the LCD temp sensor, cause seems for me that all cable I disconnected were connected again, maybe I damage one of the sensors?

Please help :-(

Same problem

Hi, Guys
my problem is the same.
So have You solved the problem?

Hello people, I had the very same problem, and I just fixed it 5 minutes ago.

After buying and installing a new harddrive (a seagate ST1000DM003) due to the previous HDD crashing, my late 2009 iMac intel (model 2374) would start but the optical and CPU fans would go up to 3500+ RPM producing a very loud noise. My temperatures were normal, and my HDD fan would be down at around 1100-1500 RPM.

edit: Running AHT (Apple Hardware Test) I got results telling me there was a hardware error:
4SNS/1/4000000: TAOP
This seems to indicate there is something wrong with the temp sensor(s).

As suspected, the LCD Thermal Sensor cable was the problem. Turns out it was inserted the wrong way!
I had over and over put the LCD Thermal Sensor cable connector with the flat all-black side facing upwards. It should be inserted with the flat side facing down.

Make sure your LCD Thermal Sensor cable is inserted correctly, isn't teared or anything like that, if you get the same problems with the optical and CPU fans going crazy.

edit:
If your LCD Thermal Sensor cable is broken you can order a new one from various places on the internet, make sure you get the one for your mac model (I think there are various ones. My late 2009 iMac model 2374 uses the cable named 922-9229).

I just wanted to chime in and say I had a similar issue with my iMac (2009) and just fixed it. I replaced the 320 GB drive with a 250GB Samsung SDD drive. After this upgrade, I could hear the CPU fan immediately after I rebooted the computer. When I looked at the fans with iStat, I saw that optical and hard drive fans were around 1200 RPM. The CPU fan was pegged at 3500 RPM.

In my case, I reopened the iMac and saw that I had pinned the LCD thermal sensor cable with one of the screws when reassembling. Fortunately, the wire wasn't broken. Just some of the insulation was stripped. I used some electrical tape to insulate the wire again. Then when I started the computer, the CPU fan was back down to 1300 or so...much quieter.

My mistake was...

I accidentally plugged the LCD temperature sensor cable into the HDD temperature sensor socket and visa versa!! Once I realized this and swapped them back, my runaway fan problem was solved!

It's actually an easy mistake to make because a) the connectors on the board fit each other b) the length of the cables make it easy to think one should go here and the other there if you're in a hurry (to be honest, I was trying to beat my fastest HDD swap time of 9min 39sec ).

Hope that helps someone among all the other good suggestions here.