What do you get if you type:
cat fan1_output
and
cat fan1_input
when the machine is running hot?
fan1_manual will be set to 0 by default, as it will be in 'auto' control
mode. I tried setting it to 1 with:
sudo echo 1 > fan1_manual
but that didn't work for some reason. However, I was able to change it by
editing the file with:
sudo nano fan1_manual
Once it is set to 1, you should be able to change the fan speed manually, by
changing the value of fan1_output in a similar way. You can change back to
'auto' mode when you're done by changing fan1_manual back to 0.