Thanks rk84, you are right. I do a test by emptying the boiler and the inserter start to work. Thanks both of you for your answer :p

Hello,

I'm actually on the tutorial 4 mission, and I don't know how to feed automatically the boiler with coal... I try conveyer belts then a robotic arm, but it doesn't seems to work.
I try to place a chest near the boiler, but it doesn't help neither...

Anyone know how to do it ?

Regards.

Umb.