Chapter 12 Air Delivery Systems 189
Copyright by Goodheart-Willcox Co., Inc.
placed under the dashboard at the rear of the firewall,
Figure 12-9. Defroster vents are placed at the forward
part of the upper dashboard so air can strike the wind-
shield. To defog the side windows, many vehicles have
small demister vents at the side pillars to direct air onto
the side glass, Figure 12-10. Air conditioner vents are
usually adjustable and may have shutoff valves. Other
air conditioner vents can be closed off by turning the
fins to the fully closed position. Vents are sometimes
referred to as registers.
Independent Vents
Some vehicles have air inlets independent of the
HVAC system. These independent vents are usually
installed on the kick panels, Figure 12-11. Ram air
fl ows through these ducts when the vehicle is moving.
A separate control is used to operate these vents. HVAC
system operation has no effect on the operation of these
vents. Independent vents are usually found on older cars,
trucks, and vans.
Figure 12-6. A typical split case used on larger vehicles. Note how the studs and nuts are used to align the parts and hold them tightly
to the fi rewall. (Ford)
Cowl vent inlet
screen assembly
Firewall
Evaporator assembly
(underhood)
Heat shield Nut and washer
Floor air
distribution duct
Gasket
Air inlet
duct
Gasket
Plenum
(pass compartment)
Figure 12-7. A modular case. All of the parts are contained in a
single assembly. Modular cases are usually installed under the
vehicle dashboard. (General Motors)
Heater hose
fittings
Refrigerant
hose fittings
Blower