You are probably running the unit at a low outdoor temperature. This will prevent the condenser from condensing properly. As a result the refrigerant is pooling up in the condenser and starving the evaporator which results in lower pressure. Lower pressure results in lower temperature hence the coil freeze up. :)

That was on another forum. Please list all conditions such as evaporator coil (clean thoroughly), condenser coil (clean thoroughly) filters changed, supply air temperature, return air temperature, dry bulb temperature, wet bulb temperature. Since this is a fixed orifice the charge is verified by super-heat, so post that reading as well. :)

outside temperature 90 F with 20 % humidity

high Low
165 40
150 25
150 23 (psi)


Temperature external of evaporator 49.5F at 23 psi (shoud be -2F)
Temperature external of condenser 97 F at the fan at 150 psi (shoud be -82.5F)

Fitting at the condenser are full of ice and evaporator his starting to fill up too.

Thank you

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