Cup fan starts and stops after boot

Siddhesh_2 · Mar 24, 2017

Hey all. My rig is 2 year old. I have a problem now. As I power on my PC CPU fan startsstarts spinning. Windows screen comes. Then suddenly only CPU fan stops. This causes CPU to overheat pc still runs but shuts down after load for e.g. games. I tried diagnosing. Reseated RAM ,CpU.Still same. For once,I disconnected my Vga cable for dry running the pc without display And surprisingly CPU FAN was on and never stopped. This also happened when I removed all rams with display(Vga) plugged. So can you tell me what is the problem. It can't be PSU since I thought it was the problem so I bought new one and it's still the same

CPU:Amd fx 8320 no overclock
Mobo:Asus M97 RE L2.0
Ram: corsair vengeance 1600hz ddr3 8 GBP
Gpu: GTX 650 2 GB
Psu: corsair vs 450w

th3p00r · Mar 24, 2017

Did you try to plug the CPU's fan to a different connection? If you did then see if you can swap out the fan with another one.

Siddhesh_2 · Mar 24, 2017

th3p00r :

Thanks for replying. No I didn't try coz there is only one CPU fan socket/slot. Rest all are for chassis

scout_03 · Mar 24, 2017

since you unplug gpa cable and it work you have 2 pci-e slot on system the second one work at 4x so put the gpu in and try to then check cpu fan spped if it does not cut you could have motherboard issue .

Siddhesh_2 · Mar 24, 2017

scout_03 :

By it worked I mean fan was moving but without display obviously cuz I removed Vga completely and left everything as it is

scout_03 · Mar 24, 2017

put gpu in second slot and plug it to monitor then check system this is to check if it is gpu or board issue .

Siddhesh_2 · Mar 24, 2017

And also I would to like mention my fan doesn't stop suddenly altogether. I got into BIOS. The speed of the fan decreases swiftly and finally becomes N/A.

scout_03 · Mar 24, 2017

then i would suspect you have a motherboard issue .

Siddhesh_2 · Mar 24, 2017

I really hope it is mobo. I have spent so much in my rig even tho it is a budget built or low end. Can't afford another cpu or gpu

scout_03 · Mar 24, 2017

did you do the gpu test .

Paperdoc · Mar 24, 2017

I suspect your fan is worn badly and close to failure. Here's what I suspect from your description.

When you first turn on, the fans (including the CPU cooler) are sent full voltage to be sure they start up. After a few seconds the system completes most of the POST self-test process and finally gets a temperature reading from inside the CPU chip, then adjusts its CPU cooling fan to match the relatively low temperature in there (because it has not run for very long). When the CPU fan gets this signal to run much slower it does that. BUT the fan's bearings may be so worn that it simply stalls at that "slow-run" setting. Then the CPU chip has NO cooling and heats up pretty quickly. At that point the mobo would try to speed up the fan, but it is stalled and needs a "high speed" signal to start up. Before it ever gets that, the CPU internal temperature goes so high the system shuts itself down to prevent damage to the CPU.

How could you test for that? The simplest test is with you finger. Shut down the system completely and open the case. With your finger, gently spin the CPU cooler fan. and let it go. If it feels stiff to spin it, or if it slows down very rapidly, the fan bearings are just about worn out and the fan should be replaced. If the fan keeps spinning and slows down slowly, it is probably OK.

If the fan is OK by this test, you might want to look closely at the way the CPU_FAN header's parameters are set in BIOS Setup. It is possible that it is set to allow a minimum speed that is too slow and you could change that.

If the fan test suggests it needs replacement, you MAY not need to replace the entire CPU cooler system, depending on its design. On many systems you can remove a few screws that fasten the fan to the heatsink without ever removing the heatsink from the CPU chip. Then you can buy a new fan of the same characteristics and just mount that in place of the old one. You might need some hints on what are "the same characteristics" if you go this route, so post back here if you need advice on that.

Siddhesh_2 · Mar 24, 2017

Did The GPU test. Still same. Ordered a new fan. Let's see

Siddhesh_2 · Mar 25, 2017

Update guys. I booted up again and got into BIOS. Cpu fan was 2209 rpm at start. Soon it gradually decreased. It was decreasing very slowly till 1000. Then it was free fall till it reached N/A. Meanwhile cpu slowly heated up and went till 80 in 5 mins. On the next start up I had "EC or EC flash got corrupted
System will shut down in 15 seconds"
Now I really think it is the mobo. ASUS gave me 2 year warranty. It's been 15 months. But unfortunately I can't find my warranty card or Bill. So I m fucked. Thanks for your help anyways

scout_03 · Mar 25, 2017

do you have a fan that could fit on the cpu cooler you could try for test and remove the stock one also for the motherboard warranty did they send you a e-mail for this or by regular mail from post office .

Paperdoc · Mar 25, 2017

I'm not clear on that last post. Was this test (good detail, by the way) done with your original fan, or with the new one you ordered? If it was your OLD fan, then that sounds exactly like a fan with worn bearings and you should not take further action until you replace it with the one you have ordered already.

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