If the fan runs, and all works for a while, then it continues to run, but no air coming out, usually means freeze up. It should be turned off when this happens. Wait an hour or so, and try again.
Now mine did this once, in the second year, thankfully in the driveway. I removed the inside cover, and found piece of duct tape had fallen and was restricting my air movement. This caused my freeze up. Repaired and all is well. Might want to pull the inside cover, and take a look.
2012 Ford F250 ext. Cab 4x4
2002 Jeep Wrangler Sahara
2008 Yamaha V-Star 650 Classic
2008 Work and Play 18LT