Over summer a friends imac started running really slow, they had just upgraded to sierra late last year and it always been slow. Then one day they noticed the fan was on full tit for ages.

They shut down for the night and left it, the next day the loading screen took ages and then stopped at 99%, they left it and the fan never came on either. They are not technically literate, and whilst I am no apple user, I offered to take a look at it.

So I tried some recovery commands, but no fixes worked, and it couldn't detect a previous OS to revert to either. They needed some data so I opened her up and removed the HDD, put it in an enclosure and we were able to restore the data to their other iMac.

Whilst I had it open I blew out the dust, made sure the fans spun freely and connected her all back up. Ii found a command that should tell the fans to come on at boot up, which they did, so that atleast proved they still worked. I tried some debug and tests that I found via google, but still no problems were found, and thus no problems were fixed, and the boot issue remains.

I forgot about it until a few weeks ago and tried again, but by then I couldn't get any of the commands to load, and then I realized the keyboard was not connecting to the imac, I changed the batteries, but I guess without the OS loading its not pairing and so I can't get any startup commands to work.

Does anyone have any suggestions? Firstly on how to get the keyboard working, and secondly on fixing the OS, any witchcraft I can apply or secret sierra commands that can diagnose and fix potential problems.

Thanks