Tech Support Forum banner

No boot: cpu fan spins but stops after 4 secs

39052 Views 3 Replies 3 Participants Last post by  Oc3an
Hi, I've already posted this issue under the "Video Card" category because at first I was experiencing what it looked like a video card problem. The post is titled "Suddenly my PC won't boot"
Following recommendations, I bought a new PSU. And now I face this problem:

I'm connecting only: a.) Mainboard; b.) PSU; c.) One memory stick; d.) Monitor to the onboard graphics on the mainboard.

Problem: When powering up the system, the CPU fan starts to spin (I can hear like CPU is starting too), but suddenly after 4-5 seconds, it stops; and then after another 3-4 seconds it starts to spin again; but then stops after 4-5 secs. This goes on and on automatically for at least 8-10 times. Then it finally gets to the POST.

Once there, everything seems normal. Then I turned it off and back on several times to see if it works, and now every time is a successful boot. Problem appears to be gone.

BUT; then after turning it off, I waited for 10 minutes (like to let it cool down). Then the problem appears again. (several failed attemps on its own to finally boot). It is like it boots when only when hot or something, I don't know.

It's important to mention that this system has been running for + or - 2 years with the PSU I had previously: Agiler AGI-PS800.

Now, the new PSU I bought is a Corsair Tx-750W completely new. The problem shows up with BOTH, so I'm discarding psu fault.

Mainboard: Biostar G3 M7 TE
CPU: Intel core 2 duo 2.8mhz
Stock CPU fan
Memory: AData 2GB

Other hardware (right now disconnected):
Nvidia GTX 260 (this was powered by a 26amp 12v rail from old PSU, the two years). (Also, this began to spin the fan at full speed when turning on, with no Post, that's when I discovered the problem) (which was the reason I bought new corsair PSU)
2 Sata HDrives
1 IDE HDrive
Card reader
DVD rom
LG 22" 1920*1080 monitor.

Last thing: I see the two memory sticks are different. One is smaller (in physical size) than the other. But the system has been working these years fine with them. The one (which I left alone to test) says: AS2667002GMU AData. The other one says: Kingston KVR800D2N6/2G. May this be the problem despite the fact that I removed one to test and problem still appears?.. MAy the problem be the mainboard? What do you suggest?

Help.. Thank you very much

Note: As I said I've already posted this issue under the Video Card category as a reply to my initial post; it's under the title "Suddenly my PC won't boot". I'm posting it here now because what at first looked like a GPU issue, turned out to be a MB, or cpu issue. So if anyone replies here or there please know it is the same issue, same person. Thanks
See less See more
Not open for further replies.
1 - 4 of 4 Posts
make sure your motherboard isnt shorting with anything.
It is very possible the old low quality PSU did some damage.
Bench Test

Remove EVERYTHING from the case.
Set the motherboard on a non conductive surface. The motherboard box is perfect for this. DO NOT PLACE THE MOTHERBOARD ON THE STATIC BAG! It can actually conduct electricity!
Install the CPU and heat sink.
Install 1 stick of RAM.
Install the video card and attach the power supply connection(s) to the card if your card needs it.
Connect the monitor to the video card.
Connect the power supply to the motherboard with both the 24pin main ATX Power connection and the separate 4 or 8 pin power connection.
Connect power to the power supply.
Do NOT connect ANYTHING else. Make sure you have the power connector on the CPU fan connected.
Use a small screwdriver to momentarily short the power switch connector on the motherboard. Consult your motherboard manual to find which two pins connect to your case's power switch. Then touch both pins with a screwdriver to complete the circuit and boot the system.

If all is well, it should power up and you should get a display. Then assemble the parts into the case and try again. If the system now fails to boot, you have a short in the case and need to recheck your motherboard standoffs.

If the system does not boot after this process, then you most likely have a faulty component. You'll need to swap parts, start with the power supply, until you determine what is defective
See less See more
You won't believe my disgrace. Haha. Have a laugh :

I did the recommended bench test; removed absolutely everything from MB, left only MB, PSU; 1memory stick & monitor to onboard graphics. And placed MB on non conductive surface out of the case.

-Using new corsair tx750w PSU:
CPU fan spins continously but no video to the monitor. No response when trying to shutdown by holding the power button (or shorting the 2 power pins on the MB with a screwdriver). Had to use PSU I/O to shut down

-Using old agiler 800w PSU:
It boots! Normally! (***)

-Then added the gtx260 video card to this setup (old PSU); and failed. Removed nvidia, worked fine. (old PSU)

-Ok; so I tested the Corsair PSU with a second, functional PC. (again: MB out of the case, only ram, cpu and monitor): It works perfectly!. Tested on that system the old PSU: worked perfectly!; added nvidia gtx to that system: worked perfectly with both PSU's.

So as you see problem on the first PC was either of 2 things: MB or CPU. But, using the old PSU, everything worked fine without adding nvidia card. It wouldn't work with nvidia card anymore.

Wait till you read this:

I was tired of this and decided to use this system without the nvidia card, and old PSU, since it was working that way. So I assembled it, put it in the case, etc. (old psu, +1 memory stick + other hardware.) Could use windows, etc, normally. Then I turned it off disconnected and added the 2nd memory stick. Turned on and... PLUM!, a little explosion and a fried electronics smell hahaha.

Checked the back MB and one of those little "streets" i dont know what's their name, those little roads that carry the info from place to place; was broken, near the memory slot. So, MB to the trash can.

Sooo, Bought new mainboard today. Also bought new memory stick.

Following this forum recommendations, placed it over the box, plugged in memory stick, CPU, cpu fan, monitor & PSU. (smile on my face)

Shorted power pins with screwdriver And............... No boot!!!!!!! hahahahahahahahaha.. (should have looked at my face...) just the spinning cpu fan, with no video signal to the monitor. :upset:
New MB; New memory; New PSU.... = F*ng CPU!!!!!!!!

Tested CPU on other compatible PC: No response. CPU Damaged.

That would be the end of my story, but just for your amusement:

Read this, my last disgrace:

There is a 3rd PC in my house, which i opened and took its cpu out to see if its mainboard has same socket so to test the damaged cpu, but it wasn't compatible; so i reinstalled its own cpu. Just removed, had a look, and reinstalled. And............... it doesn't start anymore!!! hahahaaha, no modification whatsoever to this 3rd pc, nothing!, just took out cpu and put it back again. Even bench tested it: MB out of the case, just essentials, and there isn't even a sound, a glimpse of energy, nothing. Hit the power button and nothing, nothing at all, as if it were disconnected from power source. Tried with other PSU's, nothing. it's like completely dead.

I'm gonna shot myself.
With your permission.

By the way before I do it: What do you think may have caused this 3rd PC to die completely, if I only took out the cpu and put it back in?, and now there is abslutely no response at all, no spinning fans, nothing. (functional psu's tried)

Thanks, -The soon-to-be-dead guy--

PD. Now I have to buy new CPU for the 1st PC. And I don't know if the damage in this 3rd system is MB or CPU. What do you think. haha
See less See more
1 - 4 of 4 Posts
Not open for further replies.