Air Conditioning - Ice buildup

Four days ago, my AC started blowing warm to cool air. Yesterday, an AC service man came out and checked everything and said that everything checked out. Today, not quite 24 hours later, it's not blowing cold air again. This time I went outside and checked the smaller pipe that goes into the compressor. It was covered with at least 3/4 of an inch of slolid white ice. What does that indicate? I'm having them come out again, but they may not get here until next week. I shut the unit down in the meantime.
The unit is three years old, the filters are clean, and yesterday the tech said the freon was good and the unit "amped out" whatever that means.

Thank you!

lost here that small pipe comes from the compressor. The big pipe goes to the compressor Ice on the lines .if all is clean then low on freon is next

The unit is three years old, the filters are clean, and yesterday the tech said the freon was good and the unit "amped out" whatever that means.
Sounds good: "Amped out" means the amp draw was what it should be for the unit.But did he look for a leak. Most of the time ice means the freon is low, can be other things but dont know what are when last time they put freon in it or worked on unit.

ED ;)

something intermittant like that leads me to believe the fan (indoor) may be dropping out. if the refrigerant level is ok, and the filter clean when he was there, i will bet the fan is quitting

Are you ABSOLUTELY sure it was the smaller of the 2 lines and not the larger one with the insulation on it? Smaller one iced up would be a refrigerant flow restriction at that point. Larger one iced up could be a heat exchange/air flow/refrigerant charge or metering device problem.