re: A/C unit question - line iced up

You are frozen due to low pressure caused by either a low refrigerant charge or you are not moving enough air across your evaporator. The latter is usually caused by a dirty filter, the evaporator coil is dirty, or the indoor blower motor has failed.

Check the filter first. If it's plugged, remove it and allow the unit to thaw by running just the blower. Start the unit again. If it freezes back up or if it's anything other than the filter, call a professional.