I bought an Early 2009 iMac with 2.6ghz Core 2 Duo processor. When I bought it, it was known not to boot up. It would give you 3 short beeps, 3 long beeps, then 3 short beeps. I researched this problem and found it could be a memory, memory slot, PRAM battery issue. I replaced the PRAM battery with a CR2032 battery. It did boot up once fine to the installation screen since there is a blank hard drive in it. Since that boot I only got the beeps again when trying to boot up. I have removed ram and tried with only one stick of ram, moving them between the two slots to no avail either. I then purchased a used logic board with the same specs. I swapped them out and put the ram in the slots. I got it to boot up to and install the software. I put El Capitan on the system. The software was installed without a problem. I could use the computer like normal. The computer then went into sleep mode and then would not wake up. This was late in the evening so I was tired and unplugged the computer and went to bed. I plugged it in the next morning and it booted up fine with the exception the fans were full blast right away. I turned the computer off again, then it would not boot. I press the power button and absolutely nothing happens. I let it sit unplugged for a few hours again and tried it one more time. It booted up fine again but with fans full blast again. I let the computer sit running until it went in to sleep mode again, and it would not wake again. I unplugged it and plugged it back in again and nothing happens when I hit the power button. I am at my wits end. Could it be a power supply issue? The one green led does light up when plugged in. Could it be the PRAM battery, I know the original batter was a BR2032 and I replaced it with CR2032. They both have the same physical measurements, and same 3 volts. Only difference is the BR2032 has a higher temp rating. Could it be a the power button? Any help would be greatly appreciated.