Question PSU fan not spinning, faulty motherboard or graphics card?

[jvain2005]

AMD Ryzen 7 3700x
Asus B450-E motherboard
16x2 RAM
Gigabyte NVIDIA GEFORCE GT 710 Graphics card
WD NVMe SSD 500GB

Hello All,

My system was functioning normally until it suddenly powered off on its own. Upon troubleshooting, I discovered that the fan on my PSU (power supply unit) was not running. To check if the PSU was the culprit, I attempted to manually start the PSU fan by shorting the green and black wires on the 24-pin connector using a paper clip. Surprisingly, the fan started spinning, leading me to believe that my motherboard may have been damaged.

To get a professional opinion, I took my motherboard to a service station for examination. However, I did not bring my graphics card and PSU along with me at that time. The technician at the service station connected his own PSU and graphics card to my motherboard, and everything seemed to work fine. The system displayed output without any issues. This led me to believe that my motherboard, CPU, and RAM are working fine. That leaves only two absent components, PSU and Graphics Card. I brought my motherboard back home and tried it myself, but unfortunately, it did not work.

I thought something is wrong with the connector of my PSU. To check if the PSU is the culprit, I bought a new PSU - Corsair TX550M. I attached the new PSU to my motherboard and the result is the same. The PSU fan does not spin and no lights in the motherboard. Again with the new PSU, I tried shorting the green and black wires on the 24-pin connector using a paper clip and the PSU fan started but when I attach the new PSU to the motherboard, nothing happens.

Again I had a brand new working motherboard, MSI B450. I removed the CPU, RAM, and Graphics card from my ASUS motherboard and put it in this new motherboard. Again attached the new PSU to the new motherboard and the result is the same. The PSU fan does not spin.

Now I am thinking that maybe my graphics card is the problem. However, before I go ahead and replace my graphics card, I have a question.

If I remove the graphics card (and my CPU does not have an integrated display) and keep the CPU and RAM in the motherboard, at least the motherboard should boot right? I mean I should see the PSU fan spinning and the motherboard boot up right? Or there will be no activity until I put in a new graphics card?

Considering the differences between the technician's test and mine, the only notable distinction is that he used his own graphics card while I do not have a spare one. Could it be possible that a faulty graphics card is preventing the PSU fan from spinning, thus causing the entire system to fail to power on? Should I consider replacing my graphics card as a potential solution?

I appreciate any insights or suggestions you can provide regarding this issue. Thank you for your time and assistance.

 

[Misgar]

Quite a few modern ATX power supplies do not switch on the fan (apart from a brief burst at switch on) until the computer pulls several hundred Watts.

This is variously described as Eco Mode or some other "energy saving" notation. It's designed to save a small amount of power and reduce noise when the computer is not working hard.

Most of my Corsair PSUs (750W, 850W) just sit there with the fan switched off for hours on end, when the CPU and GPU are just ticking over. On the other hand, my old TX550M runs the fan all the time.

You cannot use fan blades not spinning to infer that a PSU is faulty.

 

[jvain2005]

Quite a few modern ATX power supplies do not switch on the fan (apart from a brief burst at switch on) until the computer pulls several hundred Watts.

This is variously described as Eco Mode or some other "energy saving" notation. It's designed to save a small amount of power and reduce noise when the computer is not working hard.

Most of my Corsair PSUs (750W, 850W) just sit there with the fan switched off for hours on end, when the CPU and GPU are just ticking over. On the other hand, my old TX550M runs the fan all the time.

You cannot use fan blades not spinning to infer that a PSU is faulty.

But then how should I troubleshoot? There are absolutely no lights on MB. No display if I connect to the monitor. How do I troubleshoot components one by one? When I connected my CPU's fan, that is also not spinning. So I am like 99% sure there is no power to Motherboard.

I have a multimeter. Will that help? If so, what should I test using multimeter?

If I put only CPU and RAM - no graphics card, no SSD - then it also it should show some lights right? like orange or red? And CPU cooler fan should spin. That is also not happening.

 

[Misgar]

You could use the "paperclip" trick to bridge a couple of pins on the 24-way ATX motherboard connector to switch on the PSU, but without a proper load, it's not a representative test.

Check on line for ATX and paperclip for more details. You could measure the off-load voltages, 12V, 5V and 3.3V if the PSU starts up.

If they're within spec., then check the function of the momentary action power switch on the front panel.

If the power switch works, something else is failing the BIOS POST check. Check the CPU fan connection, memory, GPU, etc.

 

[jvain2005]

I feel stupid in writing this update and the solution.

I told you that considering the differences between the technician's test and mine, the only notable distinction is that he used his own graphics card while I do not have a spare one so I suspected my graphics card was the issue. One more difference that I missed is the power-on switch.

My PSU definitely had the issue. So I replaced it. And when I tried to power it on, MB showed no activity. So I thought something else is broken like a graphics card.

What I didn't realize is that my power-on switch is also bad. So while I kept pressing it, it didn't trigger the power-on supply.

I don't use my power-on switch on my cabinet that often. I use wake-on-lan to turn on and off my CPU. So clearly it was jammed with dust or for any other reason, it was not working. I cleaned it with compressed air and contact cleaner and now everything is working fine.

Two things I did to resolve the issue.
1) Replaced my PSU - it surely had issues with its 24-pin connector to MB.
2) Cleaned the power-on switch of my Coolermaster MB511.