The evaporator inlet line is iced up and the TCU is tripping on high head pressure – what can I do?
Ice buildup between the evaporator inlet and the TEV is a sign of a malfunctioning TEV. The ice occurs from condensation freezing on the tubing because the refrigerant is too cold. The TEV is stuck closed; this drops the pressure so much that the refrigerant temperature is below freezing. It is beneficial to test the TEV. To test the valve, pull the bulb from the evaporator outlet and immerse in hot water. A warm bulb opens the valve allowing more liquid refrigerant into the condenser; this in turn increases the suction pressure balancing the valve. Immersing the bulb in ice water reverses this reaction. If there is no reaction by changing the temperature of the bulb, the TEV is bad. Occasionally the TEV can recover. The valve may need to shock to break it loose.