LOW SUCTION PRESSURE – FROSTED LINE
Basic Problem: Insufficient Evaporator Air Flow
a. Evaporator coil iced.
b. Evaporator air flow restricted. (Dirt, bags, loose belts, damper door closed, plugged air inlets, etc.)
c. Evaporator fan motor or belt failure.
LOW SUCTION PRESSURE – UNFROSTED LINE
Basic Problem: Insufficient Refrigerant Flow
a. Low refrigerant charge.
b. Expansion valve screen restricted.
c. Restricted drier or liquid line.
d. Expansion valve restricted or defective.
e. Expansion valve adjusted too far closed (low superheat).
f. Restricted throttling valve. Pressure measured at gauge port of throttling valve below the influence of the valve.
g. Frozen expansion valve.
h. Modulation valve or ETV closed or partially closed (units with modulation.)
i. Defective Transducers.
