My a/c fan is not blowing, it is frosting up near the inlet from the a/c line on the furnace. Why is my fan not coming on?

The coil will freeze up if no air is blowing thru/across it,turn off the ac,give the ice time to melt away,till you get the motor fixed,, now does it blow when tstat is changed to heat mode? Or when you set the tstat to fan or fan only,if no ,it could be the fan capicitor but more likely the motor needs replacing