Hard Drive replacement Late 2009 iMac

While that HDD will work in your iMac, there is no way of knowing for sure if it has a compatible thermal sensor.

If not, there are two options,

1) get and use the SATA cable with/inline thermal sensor from OWC.

https://eshop.macsales.com/item/OWC/DIYIMACHDD09

2) control the run-away HDD fan using fan control software like MacFanControl

https://www.crystalidea.com/macs-fan-control

I'm thinking this,

The SL disc that you installed is only OS X 10.6.3, I believe.

You needed to use Software Update or use the OS X 10.6 Combo updater, to get your Mac back to OS X 10.6.8, before you performed your TM migration.

https://support.apple.com/kb/DL1399?locale=en_US

That TM backup was done, probably, when you were running OS X 10.6.8?

That maybe where the troubles lies.

I think you will need to use the OS X 10.6 SL install disc, again, erase and reformat the drive, again, reinstall SL from disc, then download and install the OS X 10.6 Combo Update, before you can use your TM backup.

You will first need to Format the new HDD using Disk Utility. To do that, use the erase > format > install instructions at > How to reinstall macOS - Apple Support

If it will not startup in OS Internet Recovery as described above?

Then you will need to use Disk Utility on the original Snow Leopard disc that came with your computer to erase > format and then install OS X 10.6.

Update to 10.6.8, using the > Mac OS X 10.6.8 Update Combo v1.1

Go to the Mac App Store, log into your account, select the Purchased tab and download the latest OS X or macOS version that you were on.

Then when OS starts up in the welcome window, use Setup Assistant to restore from your Time Machine backup.

The Late 2009 thru 2011 iMac's have proprietary HDD's and SATA cables.

Before buying or doing anything,

see > http://blog.macsales.com/2751-proprietary-cable-can-put-the-brakes-on-upgrading- late-09-imacs

and > http://blog.macsales.com/10146-apple-further-restricts-upgrade-options-on-new-im acs

FWIW there is a list of compatible HDDs in those articles.

If you are going to replace that drive yourself you should look at the OWC macsales site and think about perhaps installing a much faster SSD ( Soild State flash menory Drive) into your iMac, instead.

OWC macsales has these and you can call or contact them for more information.

An internal SSD in your iMac will be FAST!

https://eshop.macsales.com/shop/ssd/owc/imac-27-inch/late-2009

If you plan on doing a DIY of your iMac, if you have never did a teardown/reassembly of any computer and, especially, an iMac, you need to be careful.

Lots of different sized fasteners and small fiddly connectors to be careful of.

My replaced hard drive in my late 2009 iMac is doing what yours is doing. Finally dying a slow death after only 6 years!

I couldn't pay for both a new internal SSD and the cost for my local Apple Authorised Service to install it and I didn't want to break into my only work Mac to do a DIY I have never done before, so I went with purchasing and using an external FireWire. enclosed, 480 Gbs storage SSD from OWC macsales.

https://eshop.macsales.com/item/Other%20World%20Computing/MEF3MSSD480/

Running this external SSD from FireWire 800 IS faster than running a standard FW800 mechanical hard drive.

I am amazed how fast my Mac runs from this externall SSD. It is faster than all of my other bootable FireWire connected drives, hands down!

The only issue that I have is that the SSD enclosure doesn't seem powerful enough, even with its own power supply running it, to boot up with all 3 of my other connnected FW800 drives.

I have to disconnect all of my other drives first, boot from the SSD which is really quick and fast, then reconnect my other external drives.

If I leave the drives connected while trying to boot the SSD. I just keep getting the spinning gear forever.

That is the only strange issue I have with this drive.

Once I get everything connected up, again, things just purr along great!

OWC is an extremely trusted vendor. If you contact them and follow their advice your installation will go as planned.

However, as MichelPM mentioned going with a SSD will dramatically improve the performance of the computer. However the cost per GB is more expensive than traditional spinning HD's. Their advantage is speed and reliability. If you intend to keep your 2009 for quite some time and the only thing wrong is the HD then perhaps a SSD makes a lot of sense. Those are questions that only you can resolve.

Also, please note that working on an iMac is not easy. However OWC does provide install videos on their site and they also provide complete kits for doing the install. I strongly recommend that you get the kit and either SSD or HD from them.

My advice on this?

You really should have reinstalled OS X Mavericks, first.

Then, restored your Mavericks TM backup, then upgraded to El Cap.

I think, now, you may, in fact, have to figure out how to move individual files or groups of files from the backup.

I don't use or like Time Machine (I stopped using it way back on SL), so I am no longer an expert on what can or can't be done with an ealier Mac OS TM backup on a newer Mac OS.

I much prefer full bootable and complete system clones. This is much better for dragging files to and from old and new Mac OS versions.

BTW, you may need to reinstall or redownload any third party applications as I am NOT sure if you can simply drag applications from an older TM backup to a new Mac OS, either.

You would need to test this with a few applications to see if they launch under El Cap.

You keep jumping the gun on things.

If your TM backup was created in Mavericks, then you should have reinstalled Mavericks, first.

Good Luck on on transferring those files.