Is there a list of "APPROVED REPLACEMENT HDD" for the 21.5 late 2009 iMac that has the built in temperature sensor?

I would recommend contacting OWC (www.macsales.com) they specialize in Macs and would know which drives work in your system. You can phone them or they also have online chat sessions. If you haven't done business with them you will find many people on these forums recommend them.

Roger

I have the same iMac model. I replaced the temperature sensor cable. I tried replacing the 500GB Seagate drive the iMac came with, with a 1.5 TB Seagate and connecting the same cable as used for the 500GB. But this didn't work; the fan slowly kept going up in speed until reaching maximum speed after a few hours. So I ordered cable 922-9214 (external temperature sensor cable for optical drives). With this the fan remains at low speeds. According to sfcFanControl and SMART Utility, there's about a 5 degree difference measured internally through SMART and externally from the SMC (using the cable I installed).

What the tech guy said about replacing the drive with another one of the same brand, does not apply to Seagate drives. Off-the-shelf Seagate drives do not supply temperature data from the pins used to connect the sensor cable. These pins are a jumper block for speed selection (3 or 1.5 Gb/s) according to Seagate's documentation on the Barracuda drives.

Apple-branded Seagate drives have modified firmware, hence the added letter Q to the drive model name, so the 500GB ST3500418ASQ from Apple is not the same as Seagate's regular ST3500418AS.

Your welcome and good luck.

Just a correction to my own posts above: smcFanControl can display temperature and fan speed of CPU core, optical drive and hard drive. But the temperature is always the CPU core temperature and not the item for which the fan speed is displayed.

I replaced my ST31000528AS with an ST31000524AS at a local tech store.
While installing a fresh OS I noticed that my fan speed increased in the first 5 minutes after rebooting to a annoying max speed. At least it sounded like that. After installing the OS I downloaded an app called iStat Pro and found out that the fan speed of my HD increased from 2000 to a stunning 4500 rpm.

After some research I found a website that had made an app called HDD Fan Control. This app is specifically for this fan speed problem on iMacs. I bought it for 25 euros and I was amazed that it actually worked after installing.

The website is http://www.hddfancontrol.com/

Cheers and good luck to everyone in the world with a fan issue..

Pat

i took the optical temp sensor that is in there, cut it, and Y'd off sending signal to both optical and hd temp on MB, i soldered and used shrink tube it looks great... soon to try it, i installed a 256gig ssd and sick of HD fan @ 6000 rpm , maybe this will work...

Have ended up in the same situation as all too many others. This is a 2010 iMac and the original ST3500418ASQ was identified as failing when attempting Lion upgrade.

Having read up on all the issues, and not having AppleCare, decided to attempt replacement with the standard Seagate retail/oem version (i.e. ST3500418AS, no Q suffix), doing whatever necessary to address the fan speed issues. But on checking out our usual, more-or-less trusted suppliers, none had this drive in stock. Indeed it is getting rather long in the tooth by drive model standards and many did not list it at all. Those that listed it did not have stock.

However, there appears to be plentiful stock of the ST3500413AS. And I think this is the next-version of the original drive.

Obvious question. Does this model work in exactly the same way as the ST3500418AS? Same connector and everything else?

It feels better to be using a different model after the bad experience of the original fitted drive. Who knows, maybe Seagate have fixed the underlying issue? :-)

Rod

*** Actual Fix! *** This works,

Ok here is the skinny,

the Aluminum INTEL iMac's, 21.5 - + IF you change the hard drive you have to do this

or the fan speed will get out of control and max out at 4 to 6 Thousand RPM,

First get this! -

http://www.derman.com/iMac-Fan-Control

Next , The 2 Wire jumper that was connected to your OEM harddrive,

dont bother connecting it, even if you have the connector on the replacement / new drive

that connector is a CUSTOM jumper apple uses to get TEMP of the DISK, the firmware

on the hard drive its self has been modified to send the temp to the main board,

The solution to this is to cut the end of jumper off, the one that connects to the original hard drive

then slide some shrink tube over the wire, then strip both wires , and twist them together, and solder them, follow up with sliding shrink tube covering the exposed wire, This makes a short,

if you do not short the wire, the fan will spin out of control, you have to short the wires

in order to gain control over the fan, using iMac-Fan-Control,

Set a confortable RPM and forget about it…

you could also use a Wire Nut, electrical tape, or you could just solder-bridge the 2 pins together on the main board, but how you do it, is up to you,

ps:

even of you dont use iMac-Fan-Control, the (hd) fan will naturally just spin at a around 2000 rpm witch you cant really hear anyways, i use iMac-Fan-Control any ways, because i dont like how hot apple lets the PSU and GPU get, i like the keep them under 110F.

Note: Remember this "fix" will void any remaining warranty or AppleCare left. So before you proceed decide if that is important to you or not.

well you can flash that card all you want, but technically as soon as you open the glass in a iMac you are Voiding Apple Care,

With my "FIX" what i would do, if there was a need for apple care service, is just remove the cable before it goes in for service, but then again, there would be a different harddrive/ssd in there, so then again your Apple Care Would be voided,

i wouldnt bang your head aganst the wall over "Void Apple Care" too much, it will keep you from being productive,

have no fear.

Personally i never pay for apple care, if apple makes some junk products, then i will simply not buy apple any more, i shouldnt have to pay extra for junk hardware. it's not a 299.00 Get a dell dude failure.

technically as soon as you open the glass in a iMac you are Voiding Apple Care,

Not true at all, read the Terms and Conditions of AppleCare. You can find it at:

http://images.apple.com/legal/applecare/docs/NA_APP_English_v5.3.pdf

However doing what you are suggesting (and I'm not saying it's OK or NOT OK) does negatively affect the warranty. The warranty clearly states:

"This warranty does not apply: to a product or part that has been modified to alter functionality or capability without the written permission of Apple;(h) to defects caused by normal wear and tear or otherwise due to the normal aging of theproduct or ℹ if any Apple serial number has been removed or defaced. "

Your perogative on whether you choose to buy AppleCare is yours of course however remember other users may have a different point of view.

in the world there are do'ers and there are talkers,

i'm not a talker, apple's (NON-STANDARD) "hack" to get temp from the harddrive is annoying,

so the only to fix a hack is with another hack, like i said before it goes in for service

just pull the HD Temp cable, if you have worries, it's not like were talking about De-soldering

000 ohm resisters and over clocking, witch i have done.

Relax and enjoy the rest of your saturday!

Thank you I will and you too.