Wow....same thing happened to me just yesterday! We had the camper at the house getting it ready for our trip, and I turned on the furnace and the AC kept blowing. I forgot about the fan setting, so I ended up just flipping the AC circuit breaker. Thanks for the tip....sometimes I miss the older thermostat I had in the 2002 Sunline!!
Not only that, but I had all the ceiling vents closed, and when the AC fan ran, it made a loud high pitched noise which made me really think "oh crap, what's going on with the motor??". Turns out, it was just the air being forced through the vents....that was a relief!!