iMac does not power ON

"Hello.

Just by looking at the LED meanings, I think the first 3 LEDs mean your iMac is working properly. The 4th LED is only on when your device is in ""sleep mode"".

Hope this clears it up a little..."

"Had the same issue. Took my imac 2011 apart and put it together and it didn't turn on only the 1st led light was showing on the logic board.

The thing that worked for me was taking the ram out and putting them back one by one. Turning the machine on each time to check that each one was working

Hope this helps someone"

"I have the same symptom in this model of iMac. Just # 1 led on when computer is plugged, power button does nothing despite it shorts both power on pins properly.

Also tried removing RAM, but still fan does not spins nor beeps anyway

Reset SMC did not work either"

I hold my power button in for a count of ten or longer then press it again and it will reboot, not sure what error is causing this