CPU fan weird issue

[pcslookout]

What would cause a CPU fan to stop working or spinning sometimes only?

 

[UsandThem]

As usual, we need more info to be able to provide a good answer.

Is this a new issue? Have you tried plugging the fan into a different motherboard header? What fan are we talking about? Have you tried a different fan?

It could be a fan that is dying, a bad bearing, a motherboard fan header developing problems, your custom fan profile in your BIOS.

 

[VirtualLarry]

Try disabling "Smart Fan" in the BIOS/UEFI. That should cause the fan to run at full-speed, all of the time. Start HWMonitor, and monitor the fan RPMs over time. If it drops to zero, then you know that either the fan / bearings, or the fan header on the mobo, is going bad.

 

[aigomorla]

IT could be the bearing inside the fan has dried out.
One of the most common deaths in a fan, and one that is typically ran in a horizontal position, as the bearing lube will seep down, and dust will collect in its place.

Try spinning it by hand, do you notice resistance?
You should have almost no resistance, if you notice resistance, the bearing is done, you got dust in the fan, and under most situations its not worth it to relube it, as it will just repeat the problem over.

There are certain bearings which are more durable in the horizontal possition, but under most conditions fans like to run vertically.

 

[pcslookout]

Here is the strangest part only happens when I restart PC not when I shutdown then boot back up. Is that possible? What could it be then? Thanks

 

[LTC8K6]

I would have thought the loss of the tach signal from the CPU fan would cause a reaction from the BIOS, like shutting down or an alarm?

 

[ericlp]

in your bios... try changing the fan mode from PMW to DC. Maybe some weird signal not getting through to fan ...