I'm looking at a Carrier split system servicing the upstairs of a 3 story house - cooling coil and furnace are in attic about 22' above OD unit. The low pressure line is wet all the way to the coil in the attic and there is a large block of ice on the OD low pressure service valve. The system is about 3 years old and had been running fine until homeowner noticed that it wouldn't cool today (OD air temp about 95).

At the coil, both high and low pressure lines are wet and not cold. Any ideas on where to look for trouble?