Heres some pics of the rear of 1200:
Gary installed fans at top of roof vent opening he found that the weather will destroy them eventually. So he installed one in the lower vent opening blowing up thru chamber.
Lindsay's fans are protected because his upper vent in in sidewall of slide.
Moveup half way to see pics.
As you can see the fans are midway in the back of refer. The thermal switch maybe near top coils so you can access after removing vent cover. Others have installed where Gary did just keep away from gas burner tube.