Air Distribution System

Air distribution system

General




The air distribution system consists of:
- climate control system:
- blower fan
- damper
- filter
- recirculation throttle.
- air ducts
- vents.
Dampers control the outgoing air to:
- defroster
- the dashboard vents
- the floor outlets
- the B post vents.
Fresh air enters the climate control system through the fresh air intake under the plenum chamber.
The fresh air intake is located:
- on the right-hand side of the left-hand drive vehicle
- on the left-hand side of the right-hand drive vehicle.
Air enters the climate control system and is distributed by a large number of air vents to the passenger compartment. After circulating, the air leaves the passenger compartment via the evacuation valves in the cargo compartment.

The dampers




1. Temperature damper for controlling the heater element
2. Temperature damper upstream of heating element
3. Temperature damper downstream of heating element
4. Defroster damper
5. Ventilation damper
6. Floor damper
7. Fresh air damper
8. Recirculation damper.
Dampers controlled by damper motors are located in the climate control system.
- Electronic climate control (ECC) has five damper motors
- Manual climate control (MCC) has four damper motors.
For further information, see Design and Function, climate control module (CCM).
There are eleven different dampers controlling the air flow of the climate control unit:
- Six temperature dampers for mixing hot and cold air. Three for the left hand side and three for the right hand side. On each side one damper (2) is installed before and one damper (3) installed after the heater pad. Together (1) and (2) control the amount of air to be heated and (3) guides the warm air to the correct vent
- A floor vent for guiding the airflow to the front and rear of the floor
- A defroster damper for guiding the airflow to the front windshield and side windows.

Note! Electronic climate control (ECC) has a separate damper motor for the defroster damper.

- A ventilation shutter for guiding the airflow to the dashboard and B post
- A fresh air damper for controlling the flow of external air into the climate control system
- A recirculation damper for controlling the flow of the air in the passenger compartment back into the climate control system.
By changing the direction of the dampers in the climate control system, air is directed through the various air ducts out to the passenger compartment.
The temperature is regulated by mixing hot and cold air. The temperature dampers on the right and left sides are controlled by a damper motor each. This makes it possible to have different temperatures on the driver's side and the passenger side.
The dampers are regulated proportionally to ensure that the passenger compartment achieves the selected temperature.
The fresh air damper is speed controlled, which means that the damper reduces the size of the hole to the air inlet the higher the vehicle speed. At speeds above 60 km/h the fresh air damper closes successively. At speeds above 120 km/h the fresh air damper is nearly completely closed. The speed control of the fresh air is to keep the airflow in the passenger compartment constant, irrespective of the speed of the vehicle.

Recirculation
There are two ways for the ventilation system to draw in air:
- fresh air enters through the fresh air intake in the climate control system under the plenum chamber
- recirculated air from the passenger compartment.

Dashboard vents




There are four vents on the dashboard. Two are located in the middle at the front and one on either side.
The air flow can be regulated, fully closed or steered in the required direction using a damper. The damper is controlled with the thumb wheel located on the side of the vent. (See illustration).

Defroster vents
There are six defroster vents, two for the windshield, two for the front side windows and two for the rear side windows. The two for the windshield are designed so that the majority of the air is directed up against the windshield. The remaining air trickles out at the bottom edge of the windshield to help keep the windshield wipers free of ice.
The air ducts to the front side window defrosters are a continuation of the windshield ducts.
The air ducts to the rear side windows go via the floor to the B posts. The air ducts are a continuation of the windshield ducts.
The defroster vents in the B posts can be adjusted by the rear seat passengers.
The seven seat XC90 has two additional defroster vents, one in each C post. The air to the two additional defroster vents comes from the XC90s rear climate control.

Floor vents
There are four air vents in the floor (seven seat XC90 has six air vents).
Two are positioned under the respective soundproofing panel, one on each side of the center console. The other two are located one under each front seat and face backwards.
Seven seat XC90s two additional floor air vents are located on the left and right hand sides below the center row of seats.

Evacuation valves




In 4-door vehicles, the air vents are located at the edge between the parcel shelf and the rear windshield. The air goes from here through the cargo compartment and on out through the air vents behind the rear bumper.
In 5-door vehicles, the air passes directly out through the air vents in the cargo compartment.
There are rubber flaps in the air vents. The flaps open when the air pressure is higher in the passenger compartment that outside. When the air pressure is the same on the inside and the outside, the flaps close. This prevents water and air (odors, dust and exhausts fumes) from penetrating the passenger compartment.