Fan only comes on sometimes mainly whenever I restart pc but always when I shutdown and power back up (cpu fan only)

[timltimmy]

This is for the cpu fan only. What could be the cause or issue? Could it be a serious issue?

I always had this problem with my pc but always double and triple check the cpu fan is running before I keep my pc running. Mostly never restart. Always shutdown then power back up. Just so I don't have the problem. Know restarting can be important sometimes. Though a shutdown and boot back up is basically the same thing. Just not as convenient.

It is so weird. PC is like 2 or 3 years old about. Maybe a little older not 100% sure sorry.

[timltimmy]

The best thing is my BIOS always alerts me with a warning when cpu fan does not come on. So I can always shutdown immediately after booting into the login screen of the os and power back up to fix it every time.

I know this should not a be a issue to begin with.

[_I_]

some boards will turn off the fans when not needed
at idle and cool
if its under a load and does not turn on then there are problems

newer cpus will throttle and work even without a cooler or fan

[Baker]

I had a gigabyte mobo that did this. I set the CPU fan for 100% in the bios and it minimised it but it sometimes still happens occasionally.

[timltimmy]

It is a Asus mobo but sure it could happen for this brand too!

Thank you both!

[Carlsberg]

Did you verify the fan is plugged correctly into the correct header on the board?

[timltimmy]

Originally posted by Carlsberg:

Did you verify the fan is plugged correctly into the correct header on the board?

Yes.

[GOD RAYS ON ULTRA™]

Shutting down doesn't clear your ram. Restart clears the ram and that's when the pc has to reload files from storage to ram. This takes cpu power, which is why your fan comes on more with restart vs a shutdown.

[_I_]

by default no, shutdown hibernates
restoring the last session on startup again

restart does a clean boot

[Illusion of Progress]

IIRC, during a "restart" versus a fresh boot, the motherboard may skip some things.

You say a cold boot always starts the fan, but a restart sometimes doesn't. Does this mean the fan is already off when restarting, or does it go from on to off during the restart? Does the fan start up later if the CPU gets warm, or is it "stuck off" once it's off?

If it's NOT stuck off, this isn't necessarily concerning behavior.

Originally posted by Hardware Hero™:

Shutting down doesn't clear your ram. Restart clears the ram and that's when the pc has to reload files from storage to ram. This takes cpu power, which is why your fan comes on more with restart vs a shutdown.

I may be wrong on some nuances here, but...

RAM is volatile storage, so it just needs to lose power to be "cleared" per se. Both shutdown and hibernate should theoretically "clear" the RAM all the same as both actually turn the PC off proper, so they will both need to populate RAM again upon next load. The difference is, with the default Windows 8/10 shut down behavior, it's still closing all your programs, but otherwise basically saving a snapshot of the Windows kernel to be read from upon next boot. This is similar to hibernate (but hibernate proper will not close your open programs and will retain your current workflow, but it will need much more disk space and take longer).

Sleep mode, by contrast, "suspends" the PC; that is, RAM, and pretty much only RAM, is kept fully powered while in sleep mode and everything else stops (that is, CPU clock generator turns off, so no "processing" is occurring, and everything else, or at least almost everything, including fans should turn off [though it really depends on what S states are supported and enabled]). This is why sleep mode is generally so much faster than anything else while also retaining your exact moment of closure; nothing has to be written to, and read from, disk to RAM as RAM just retains it's current contents and presents it upon awaking, whereas both Windows 10 default "shutdown" behavior (hibernate) and restart do have to read SOMETHING from disk to populate the empty RAM. The drawback of sleep mode is using more power (but it's very minimal) and needing to keep power supplied (so, no good for laptops or if going to be unplugging the PC).