I bought a ST32000641AS for iMac27 Late2009, which had a ST1TB. The new HD didn’t bring the temp. cable so the original was used. Now after 1/2h the fan revolutionizes at high speed causing noise and don’t know if will cause another problem. What can I do

You need to use a HD that has an integrated temp sensor in it. You may want to contact OWC (macsales.com) to see if they have a drive that will work. Beginning in 2009 Apple began using drives that have integrated circuitry (including temp sensors) in them which means that unless you are willing to do some hacking of your hardware you need to use drives that are designed for your machine.

I tried replacing the 500GB Seagate ST3500418AS with a 1.5TB ST31500341AS my late 2009 21.5" iMac, as OWC's article recommended this drive. But the same problem with the fan running at full speed. So I put back my old drive again.

Apparently what OWC is saying about the temperature sensor connector on the drive is not correct, at least not for Seagate drives. This connector is only used for reading the temperature in Apple-branded drives with customized firmware. With regular Seagate drives, the same connector is actually a jumper block for speed selection. See page 20 of this document: http://www.seagate.com/staticfiles/support/disc/manuals/desktop/Barracuda%207200 .11/100452348b.pdf

The solution is to replace the brand-specific temperature sensor cable with the cable from the older iMacs used for attaching externally to the drive. I have ordered this cable (part number 922-9214 for my iMac model) and will install it together with my new drive once I receive it.

I try to replace a bad hard drive on a 09 iMac. I tried a few different options as stated by OWC, the only solution that worked was replacing the drive with an Apple drive from an iMac I purchased on eBay.

Before you bought from OWC did you call or chat with them to see if the drive was OK in your machine? If you did you're right they goofed, if not you probably should have to confirm the drive would be OK.

Just an update to my own post above. I received the cable a couple of days back. I replaced the 500GB Seagate drive provided by Apple with a new 1.5 TB Seagate drive. (Both drives are Barracuda 7200.12 drives.)

I also replaced the original temperature sensor cable connected to the 500 GB drive with the 922-9214 and affixed it to the body of the new drive.

The cooling fan remains silent. Two passes through AHT finishes without errors.

So with this I conclude that the discussions about upgrading a hard drive in an iMac can be done if you choose a drive from the same brand and family, does not apply to Seagate drives. Apple-branded Seagate drives are modified to allow reading temperature data from the speed jumper block.

But this comes up as the optical drive sensor cable. I wonder if it will calibrate properly with the SMC to read the drive temp and ramp the drive fan up accordingly?

I have both sFC (smcFanControl) and iStat Pro running on my iMac. I am assuming that sFC reads HDD temperature from the SMC, now coming from the cable I installed, and iStat gets its data via SMART. sFC and iStat report a difference of 5 degrees on average. Right now sFC says that my hard drive temp is 42 degrees, while iStat says 47 degrees. That would be explained by the SMART data being measured inside the drive case, where the temperature should be higher.

I live in Muscat, Oman and the ambient temperature in my living room is around 25-29 degrees Celsius (77-84 in Fahrenheit), so the iMac will get a little hotter than in cooler climates.

I would have thought they'd both be reading off the same sensor.

What does Temperature Monitor show? It's highly regarded for accuracy.

I downloaded SMART Utility from Volitans and it shows the same temperature as iStat. And a tool called smcFanControl sounds like it is getting its data from the SMC. The fact that sFC shows slightly lower temperatures is to me a sign that its getting the external reading through the SMC.

Temperature Monitor v4.94 clearly says that its data is taken using SMART.

(SMART Utility says that I already have two bad blocks replaced on my brand new 1.5TB Seagate?! True or scareware tactics to convince me to buy the full license so I can keep monitoring the drive? If the drive is really dying then I can at least install any drive with the external sensor cable.)

Not sure how to answer, but you could read this article about bad blocks on new drives. And there was a recent discussion, with no agreement, on zeroing new drives to eliminate bad blocks. Can't locate it right now but this is where it was.

https://discussions.apple.com/community/mac_os/mac_os_x_v10.6_snow_leopard?view= discussions#/?per_page=50

Warning: Bad sectors on a modern hard disk are almost always an indication of a greater problem with the disk. A new hard disk should never have bad sectors on it; if you buy one that does have bad sectors, immediately return it to the vendor for exchange (and don't let them tell you "it's normal", because it isn't). For existing hard disks, the vast majority of time, a single bad sector that appears will soon be accompanied by friends. You should make sure to contact the vendor if you see bad sectors appearing during scans and make sure the data is backed up as well. Personally, I will not use any hard disk that is developing bad sectors. The risk of data loss is too high, and hard drives today are inexpensive compared to the cost of even an hour or two of recovering lost data (which takes a lot more than an hour or two!).

http://www.storagereview.com/guide/formatDefect.html

To put what Smart Utility says in perspective. I ran it on my then new 21.5 and it produced a lot of gibberish. I'm not sure what to make of the report you got.

Message was edited by: WZZZ

I know that hard drives have a limited number of spare blocks, and once these are used up, the drive will fail. And my experience with servers over the past twenty or so years says that this can sometimes happen very quickly. Once a servers starts logging BBR errors then you need to plan for a replacement.

I'll get a new drive and watch the BBR count. If it goes up any more then I'll replace it.

Sorry for wandering off topic 🙂

A correction to my own post 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.