@stigzler I mean /usr/bin/python /recalbox/share/system/fanControl.py & so that the process goes to background in multiprocessing. Otherwise you just lock the init script and never give the hand back.

What is your python script ? you should, for debug, run your script in custom.sh like /usr/bin/python /recalbox/share/system/fanControl.py 2>&1 | recallog & and see what the recalbox.log mentions