What's new

Fans running at full while locked and idle


I have frequently returned to my locked, idle Surface Book after being away for an hour or more to find it is running its fans at full speed. The screen is off and it should be doing nothing.

When in this state, it is slow to respond to any form of wake-up signal. Ultimately, once unlocked, the fans will turn off, suggesting the process that had been using the CPU has ended. I've not yet been mindful enough to have Process Explorer tracking what's going on, but I'm curious if others have seen this behavior and already have some troubleshooting to share.



Well-Known Member
The screen is off and it should be doing nothing.
That statement is incorrect. It's in connected standby, which is exactly what it means. The screen may be off but active apps may be doing something and struggling to do it. Try closing all your apps to see if it still does it.


Okay, well, yes. That's the problem. I as the owner of the PC don't expect it to be doing anything, but clearly something is working very hard when I feel the computer should be idle.

I've got Process Explorer open to see if I can get a capture of the process that's using a bunch of CPU resource for the next time it happens.


I was able to trace the offending process: LockAppHost.exe. Here is what it was doing to the CPU while my Surface was locked with the screen off:


You can see how it immediately surrendered the CPU when I unlocked the PC at the right side of the timeline.
Search tags for this page
cpu fan locked at full speed
cpu is busy while computer is locked
fan running full speed at idle
fans running at full speed idle
lockapphost cpu
surface fan running full speed
surface fan running while idle
surface pro 4 utilization while locked

what does lockapphost do

windows 10 standby lockapphost

Staff online

Members online