Just another bit of info on the Jenn air fan.
I have the left side of our Jenn air set up with the griddle. As has
already been said, the fan comes on automatically when the griddle is lit.
I had assumed this was because we had replaced the grille with the griddle -
and that the fan was necessary when cooking on the grille.
Therefore, I thought the automatic fan was not needed for the grille. I
took off the front face /trim cover (take off knobs, take off face plate),
identified the wire that ran the automatic fan switch and disconnected it.
Sure enough, the fan no longer ran automatically when I lit the griddle.
The unfortunate part was that the griddle burners didn't really work
properly without the fan running - it seems like the fan (suction) pulls air
throught the space between the burners and the griddle and thus helps it to
burn properly. I re-installled the automatic fan wire and the burners
worked much better.
Just fyi, fwiw.