My PC has suddenly stopped starting up. On checking with case open, the CPU fan starts running when the power is turned on, but it stops after about 2-3 seconds, restarts again after about 2-3 seconds and the loop is repeated. There is no beep and nothing appears on the screen. On searching the internet, I found there could be several reasons for this. I tried removing hard-disk, CD drive, tightening connections etc but of no avial. I also tried using a new power supply but the response is the same.

Where could be the problem and how can it be solved? Thanks in advance.

Update: The problem could not be corrected and I had to replace both the cpu and the motherboard.

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4 Answers

Having checked a different known working power supply and without any other information, (do you have any LEDs on the board that blink when starting up?), I would suspect a failed motherboard component. To fully test the board remove everything except the CPU, one stick of RAM and the power connectors. If it starts like that try again with the others stick(s) of ram one at a time then all together. If it fails to start with any one stick then it's bad RAM. If you come up with anymore information we can work from there.

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I have seen such behavior when the power supply wasn't up to the job. The voltages fail to stabilize and the system shuts down.

Recently ran into this trying to build a gigabyte Z77h-dsh3 motherboard and i5 E3579J CPU. It turned that one of the tiny pins in the mobo CPU socket was bent. Checked them with magnifying glass and carefully straightened it out. Everything works fine now.

I had the same problem of CPU fan turning on and off and the PC never booted up. At first I thought it was the power source unit or CPU problem. It turned out the RAM card is faulty. After changing the RAM card, everything worked fine.