Some Sonata (YF) vehicles may develop a condition with the separator plate in the
middle of the heater box (Heater & Evaporator Assembly) becoming warped and may cause
interference against one or more of the internal flaps that control air flow to the vents.
This condition may result in HVAC system exhibiting abnormal noise from the heater box, difficulty to
control the vented temperature, blocked airflow due to improper mode control, and/or airflow stuck in
defrost mode.
