I have a 2009 A1312 iMac I am trying to get fixed but I can't really figure out what the problem with the OS loading. I have tried multiple HDD's however all seem to get stuck at the apple logo with 75% loaded. I think the reason the fans are 100% are that there is no OS found and the LCD temperature connector is broken. Could the broken connector on the motherboard be causing the OS not to boot fully on a HDD which is not the original one for the system? I have been able install the OS on the HDD's on the system however I cannot boot into the OS.