Lotus 2004 ELISE Service Notes page 388

Lotus Service Notes
PL.2 - HEATER/A.C. AIRFLOW OVERVIEW
The major units of the Heating Ventilation and Air Conditioning (HVAC) system comprise a dual intake
blower fan, an evaporator housing (with no evaporator fitted for non a.c. cars), a heater housing and an airflow
distribution unit. The fan blower unit and the combined evaporator/heater unit are mounted in the chassis
climate chamber ahead of the cabin footwells, with the airflow distribution unit mounted on the top of the
chassis scuttle area. Ambient air is collected from the radiator air intake duct via two ports in the radiator
ducting, which mate to apertures in the chassis front crossmember. Moulded ducting on the rear side of the
chassis front face directs this air, via a shut off butterfly flap valve on a.c. cars (to provide a recirc. function), to
the blower fan front intake. The rear intake of the double sided fan housing is connected to perforated ports in
the front wall of each footwell.
The fan blower unit directs all airflow through the a.c. evaporator (if fitted), after which a pair of linked air
blender flaps, control the proportion of air which flows through the heater matrix. The upper flap is driven by a
stepper motor from the cockpit temperature selector, with the lower flap linked to the upper by toothed belt.
After leaving the HVAC chamber, air is ducted to a distribution chamber mounted on the top of the chassis
scuttle which distributes air to screen, face level vents and footwell vents. The distribution chamber contains
a horizontal, three vane, rotary flap, driven by a stepper motor, and controlling outlets to the screen and face
level vents. A link rod connects this flap to a second flap controlling airflow to the footwells. Ducting for the
windscreen vents is incorporated into the underside of the fascia top panel.
Schematic Airflow
Windscreen
vent
Footwell vent
Blower fan
A.C. evaporator
Re-circuation flap
(a.c. cars only)
Crash structure
Fresh air in
Section PL
Face level
vent
Re-circ. ports in
footwell
Heater matrix
Stepper motor for
re-circ. flap
Chassis front wall
p101
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