Technical Bulletin (Whistle Noise from Center Vent Area; Blower Set On 3 or 4 with Full Heat Selected):
Customer may hear a high pitched whistle when the Climatic temperature knob is on full heat and the blower is set to either 3 or 4. The temperature flaps allow air to escape past the temperature flap seal. The production solution for this issue was Introduction of improved air distribution unit.
