# Laptop fan blows on and off in a pattern



## Tangaroa (Jan 6, 2015)

Observed laptop fan behavior in both FreeBSD 10.1 and PC-BSD 10.1:

1. Fan blows for ten seconds. 
2. Wait for twenty or twenty-one seconds.
3. GOTO 1 

This pattern repeats until the system is shut down. 

This always occurs when running from the console.

This almost never occurs when running from KDE, but has been seen once. There must be some power management feature in xorg or KDE that places the fan under control.

This likely has no relationship to cpu temperature. When this is happening, `sysctl` places the cpu temperature at 40 - 49 degrees C. For comparison, the temperature is 47 C when this is not occurring. Regardless, this pattern is seen when the system is idling at console and nothing is running.

Could someone explain what software component controls the fan, why a choice of user interface would have any effect on the issue, and what some possible causes of this issue might be?


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## Amzo (Jan 6, 2015)

Have you tried looking into powerd(), I also found this https://github.com/darklightclod/bsdfan

Using a combination of both I would presume will solve your issue.


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## uzsolt (Jan 6, 2015)

I think it's because of GPU. I've a laptop with Radeon card. When I don't want always hear the fan I should use 
	
	



```
Option ForceLowPowerMode "on"
```
 in xorg.conf. On console doesn't help anything as I know.


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