Chosen Solution
My power button on my 27 inch imac late 2009 model works intermittently and the problem is getting worse over time. When it isn’ t working it depresses and makes a faint click. Sometimes rotating my finger on the button helps but usually not. When all else fails I can invert the imac and then the button works fine. I have no idea why flipping it upside down helps but it does. But the imac is heavy and this technique is getting old. Does anyone know how this button can be repaired or replaced and what it costs? I am not intending to fix this myself.
From your symptoms I’m not sure if the power switch its self is bad or the power supply. At this point I think you’ll need to bring it in for an estimate at an authorized Apple service center. They should be able to give you a better idea which needs replacing here. In either case it’s a bit of work to pull the power supply as well as gain access to the switch unit which is under the speaker.
