Question Fan only runs when screen is on ?

Jan 22, 2023
6
0
10
When the screens are blank because the screensaver is running the PC is silent, but when the screens come to life the CPU temp sensor reads 100° C and the fans roar to life. This is on an Alienware Aurora R5 Desktop rig.
 
Jan 22, 2023
6
0
10
So to recap. I step into my office, the screens on my Alienware desktop PC are blank (screensaver), no fan noise. I wiggle the mouse to turn on the screens and within a couple of seconds the box fans turn on full blast and the CPU temp reads 100 C°. After a minute, the CPU cools to about 60 C° and the fans turn off.
 

Paperdoc

Polypheme
Ambassador
First, I suspect that fans do NOT "turn off", but that is possible. What MAY be happening is that when they are running slowly they are so quiet you do not realize they are still running.

This MAY be what is going on - it applies to certain CPU chips (not all). SOME recent CPU chips have an odd quirk. When they go from idle to some increase in load their internal temperature sensor for a brief few seconds detects a very high temperature, then the temp settles back to perfectly normal. For that brief time the CPU_FAN header responds to that high temp reading by speeding up the fan, then slows down when the temp reading goes down again. The ACTUAL temperature spike is normal, brief, and harmless, so there is no reason to worry. I do NOT know whether this apples to YOUR system.
 
Jan 22, 2023
6
0
10
Paperdoc thanks for your answer. It's been a mystery to me for longer than a year and this is the first answer I've gotten. Yes I think the fans run quietly after the initial blast. I've always assumed that the CPU heats up while the screensaver is on but it's not detected until the screens wake up, which is not a healthy thing to be happening to my PC. But I've never seen any il effects. I'm not going to worry about it for now after your explanation. Thanks!