Subaru 2002 Impreza Service Manual page 372

HEATER SYSTEM
HVAC System (Heater, Ventilator and N C )
3) Heating (HEAT) mode
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Warm and cool air flows are created by structural means, namely, by forming sealing surface
for air toward leg area on the heated air passage side and that for air toward the defroster (DEF)
outlet on the cooled air passage side.
To prevent an excessive difference in the temperature between the two air flows, a bypass pas-
sage is provided to allow part of heated air to flow toward the ventilation (VENT) outlet.
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To maintain the passage toward the defroster (DEF) outlet even during the heating mode opera-
tion, the door of the passage toward leg area is fully opened to the make the passage also serve
as a passage toward the defroster (DEF) outlet.
DEF
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NF0165
(1 ) Evaporator
(2) Bypass passage
(3) Heater core
4) Defroster (DEF) mode
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Air passages are designed in such a way that air flow resistance is minimized and defrosting
performance is maximized.
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The air passages toward the defroster (DEF) outlet is long enough to ensure a same airflow rate
at all defroster outlets.
DEF
(1) Evaporator
(2) Heater core
NFOl66