Laptop fan "revs up" when screen turns off

Hungerdunger

When I'm working on my Dell Inspiron 17-5770 the fan is only just audible.  I have it set for the screen to turn off after 20 minutes of inactivity, and within a minute or two of that happening the fan speeds up and is quite loud.  This continues until either I start using the machine again or it goes into sleep mode.  This has been happening for about 4 - 5 weeks, even if I shut down all running programs first..

A Google search didn't come up wih a solution to this particular problem so I'm wondering if anyone here can suggest why it should be happening and whether I can cure it.

Newcad

I believe that what is happing is that when your screen turn off you you are obviously not using the computer and it is in 'idle' mode, at which point Windows notices you are not using it so starts doing it's needed background housekeeping.

It's that background work that is using the CPU a lot, the CPU gets hotter and so the fans ramp up to cool it.

If/when you start using it again then the Windows housekeeping stops.
The same if/when it goes into sleep, the Windows housekeeping stops.
But because it hasn't finished then the next time the machine goes idle it will start housekeeping again.

I suggest that you let the housekeeping complete.
Set sleep to 'never' and just let it go idle and the housekeeping start, then let it run for a couple of hours and tidy up what it wants to, at which point it will stop and the fans will quiet again.
Do it overnight if you want, just turn sleep to never and leave the computer on and logged into Windows overnight.

Once Windows has done it's stuff and cleaned up what it wants to then your computer will not have to try and do it in smaller bits each time that it goes idle again.

I usually let my computers sit switched on but not being used for an hour or two each month, so that Windows can do all it's background housekeeping undisturbed.

Hungerdunger

That's an interesting idea that hadn't crossed my mind.  I'll try it tonight and see what happens.

facade

My PC- not a laptop is on 24/7 365 days a year.

I happened to still be up at 2AM this morning (!!!!!) when I heard the fans rev up to high speed, so it obviously had a sweat on.

Rushing over and waking it up I did a quick Ctrl+shift+esc into the task manager and found 80% CPU use on a task which it turns out had scheduled itself to run at 2AM- presumably so as not to slow it down when I might be using it.

Windows schedules maintenance and updates for the wee small hours as Newcad suggests, which doesn't happen because you switch it off, so when it is overdue enough it starts as soon as it can when it thinks it is on but not being used.

Hungerdunger

UPDATE:  As suggested I left the laptop running overnight with sleep disabled (about 14 hours in total) but it hasn't cured the problem.Does anyone have any other suggestions?

km1500

high fan speed user indicates high CPU usage because it gets hot

are you able to look at task manager and see what is using the CPU when the fans are revving

bob2302

Turn-off screen blanking and leave Task Manager running maximized and with processes sorted by CPU. That will tell you the cause.