A customer complains their air conditioning system runs constantly but does not cool well, the suction line is very cold and the compressor is sweating. The most likely cause is:

• A. A restriction of the return air or a dirty evaporator
• B. A refrigerant leak
• C. A faulty thermostat
• D. A dirty condenser coil

Answer: (A)

When the evaporator isn’t getting enough air, the coil can’t absorb heat from the space, so the refrigerant stays very cold as it evaporates. A restricted return path or a dirty evaporator reduces airflow across the coil, causing the system to run continuously in an attempt to reach the setpoint, while the suction line remains very cold and the compressor sweats from the cold, humid surface. This airflow issue best explains a constant run with poor cooling, whereas a refrigerant leak, a faulty thermostat, or a dirty condenser coil would produce different symptoms.