Taken from the Dometic thermostat users guide uploaded by Triguy. You can find many helpful guides (including thermostats by Hunter, Honeywell, and Coleman), using the library tab near the top of the Forest River forums pages.
“Furnace” - Furnace Mode
In this mode there are 3 fan speed selections:
Lo - (LOW): The fan operates continuously at low speed.
Hi - (HIGH): The fan operates continuously at high speed.
Au - (AUTO): The fan will be OFF.
Note: If additional indoor air circulation provided by the air conditioner
is not desired during Furnace Mode of operation, select Au
(AUTO) in the Fan Mode to shut the air conditioner fan off. If Lo
(LOW) or Hi (HIGH) is selected the air conditioner fan will continue
to operate on the selected speed.
EDIT: Fonzie and Wiscampsin already answered while I was looking.
2011 Flagstaff 831 RLBSS
I've just ordered a chicken and an egg from Amazon.... I will keep you posted.