9000 Front A/C

There Are Three Designs Of The Heating And Ventilation Unit
1. Heating and ventilation unit.
Manually controlled heating and fresh air unit.

2. Heating and ventilation unit with A/C.
Manually controlled heating and fresh air unit with additional A/C and recirculation.

3. Automatically controlled heating and ventilation unit, ACC.
Heating and ventilation unit with automatic climate control meaning that the unit automatically maintains the desired cabin temperature irrespective of the temperature of the air outside. The design of the control panel varies slightly between year models.





Heating, Ventilation Part
The design of the heating and ventilation part is common to all three units. When the air has entered the unit through the air intake beside the lower edge of the windscreen, it passes through the fan housing and is directed by the air-mixing damper through or past the heat exchanger. Using air distributors, the air is then directed to the desired vent. The system is an air-mixing system.





Air Distribution System
From the heating and ventilation unit outlet, the air is directed via air ducts to the various vents, which distribute the air in the cabin.

- Floor and defroster vents. There are four floor vents, of which two are for the rear floor. On year model 1988, front floor ducts were added with four separate air vents as well as rear door fans (not illustrated) for demisting the rear windows.

There are six defroster vents. Two of these control air to the windscreen and four small vents on the dashboard direct air to the front windows.

From year model 1987, chassis number Ch1007949 for left-hand drive cars and chassis number Ch1024270 for right-hand drive cars, all defroster air for the side windows is concentrated to the vents in the loudspeaker grills.

- Air vents in the facia. There are four air vents in the facia. These can be individually controlled and the direction of air flow can be regulated both vertically and horizontally. The vents in the facia have a control which allows air volume to be continuously controlled.





Air Distribution
A certain amount of air is always directed to the defroster vents in order to keep the windscreen and windows free from mist. The air distribution control can be regulated to a number of detent positions between the four main positions.

- Position 0
All vents closed. No air distribution. No power to fan motor. Despite this, there may be a draught when the car is driven. The air is forced in through the system by wind pressure.

- Ventilation position
Air from vents in facia. Small amount of leakage to defroster vents (felt at high fan speed). Selectable fan speed.

- Floor position
Air from floor vents. Small amount of leakage to defroster vents (felt at high fan speed). Selectable fan speed.

- Defroster position
Air from defroster vents. Small amount of leakage to floor vents (felt at high fan speed). Selectable fan speed.





Air Conditioning System (A/C):
- 1-Desiccant container, 2-Evaporator, 3-Condenser and 4-Compressor.

- The function of air conditioning in a car is to lower air temperature in the cabin to a comfortable level when outside temperatures are high.

- In humid weather, the system can also keep windscreen and windows free from mist at low fan speeds, even in difficult conditions.

- The air conditioning does not produce cold, but removes heat from the car cabin.

- In order to conduct heat away from the cabin, a refrigerant is used which has a lower temperature than the air as heat always moves from a warmer object to a colder one.

- The refrigerant used is a fluid, R134a (R12 in older year models), which boils and evaporates at low temperature about -3O °C (-22 °F) at normal atmospheric pressure.

- The refrigerant has a constant ratio between pressure and temperature meaning that if, for example, pressure is changed, temperature also changes. This applies as long as volume is constant.

- This relationship is used in the air conditioning by allowing the refrigerant to circulate in a closed system and changing its pressure so that temperature changes and it boils (evaporates). At system pressure, the refrigerant boils at about 0 - 4 °C (32 - 39 °F).

- In order for the medium to boil, heat must be available. This heat is taken from the air around the evaporator in which boiling takes place. When heat is absorbed by the refrigerant, the surrounding air becomes colder. It is this cold air which is blown into the cabin by the heating and ventilation unit fan. The heat which is absorbed by the refrigerant in the evaporator is transported to the engine compartment where it is transferred to the air by a condenser which is cooled by the air blowing through it and/or the electric radiator fan.