A while ago, I asked a question wondering what this thermostat was (see attached picture). I found out that this controlled the Fantastic fan in our kitchen area; I assume you have one or two of these in your rig.
If you have the same device, if you put the lever all the way to the bottom it will turn off the auto fan.
2005 Monaco Cayman 36PDQ
Toads: 2018 Equinox, 2008 HHR or 1993 S10 with ATV in bed