The cause of a suction line frosting is that the saturated temperature of the refrigerant is below 32 f degrees. The evaporator coil could have an ice build-up, from not defrosting properly. Or the unit is low on charge. Frosting is a sign that the evaporator pressure is low enough to flash the liquid off, but not enough air flow to let the refrigerant absorb the heat in the freezer.
If the system was overcharged enough to make the suction line start freezing, the compressor would of been dead by now.