Comment # 10 on bug 1040718 from David Rankin

The fan-on/heating issue is due to some interaction between the nvidia driver
and Firefox 45.9esr. When the display goes to sleep, if FF is left focused,
every 10-20 minutes, the GPU temp is driven above the 52 deg. fan-on limit and
the fan kicks on and it cools the system down to below the 45 deg. fan-off
limit. If FF is minimized, or focus left on another app, then the GPU temp
never exceeds 44 during sleep (it wanders between 36=44 deg., for whatever
reason, but never gets close to the fan-on limit) So this issue is not related
to the sysfs interface.