Recently we did a teardown on a 2009 iMac with a literally dead hard drive (it wouldn’t even see it when connected eternally). After various tests and second opinions we can do this conclusion the hard drive was completely dead and will not work anymore.
We decided to open the machine and replace the drive and make sure everything was up to par, what we came up with, in conclusion to, was the factor this computer was having overheating issues as well.
Once we got everything put back together we started also having issues with video not coming on. We ended up having to replace the inverter cable (not a very cheap cable) in order to bring it back alive.