Chosen Solution
iMac powers on irregularly when pressing power button. With iMac powered off, Led #4 blinks. If I press the power button when Led #4 is in the off state, nothing happens. If I press the power button when Led #4 is in the on state, the machine will power up, and operate properly. I have changed the power supply and power button. Any ideas why this may occur?
LED #4 is indicating the LCD is connected and working properly. Check both ends of the LCD connection. Check the pins and cable for damage. If the cable looks fine, disconnect the LCD and try with an external display. See if the machine powers on with it disconnected.
