I seek troubleshooting help with this MacBook Air2,1 (Mid 2009) that my brother gave me. On average, it will only boot up one out of 20 attempts. Here's what a failed boot attempt is like: Push the power button. The "sleep mode" light in front glows (not fluctuating in intensity) for 10 seconds, then goes off for 3 seconds, then glows again continuously until I turn it off with the power button again. I hear the cooling fan run when the sleep mode light glows. The cooling fan has a loose bearing, I think, as it sounds as if one of the fan louvers is striking something during rotation. No other things happen. No lights under the keyboard. Nothing appears on the screen. This runs El Capitan.