HVAC - Design & Function: Other Volvo V70 II

Air cleaner passenger compartment, replacing (2001-2004)

V70 2000

1. See «Air cleaner passenger compartment, replacing»(ref-406998-S13084303262011070100000) .

Scheme 1110

There are five main components in the climate control system

1. evaporator
2. receiver drier
3. compressor
4. condenser
5. expansion valve.

The system is filled with a suitable quantity of refrigerant and oil. The role of the oil is to lubricate and seal the compressor (piston and cylinder).

A fluorescent leak-tracing agent is added to the refrigerant. The leak-tracing agent makes it possible to trace leaks using UV light.

Scheme 1111

Included in the climate control system

1. Compressor
2. Condenser
3. Engine cooling fan (the same cooling fan used by the engine cooling system)
4. Receiver drier
5. Expansion valve
6. Evaporator
7. Blower fan.

Explanation

A - High pressure, warm fluid

B - Low pressure, cold fluid

C - Low pressure, cold gas

D - High pressure, warm gas

Dark arrow - Warm air

Light arrow - Cold air

The system is divided into

1. a low pressure side (B, C)
2. a high pressure side (A, D).

The two sides are separated by the compressor (1) and the expansion valve (5). The evaporator (6) is located on the low pressure side and the condenser (2) is on the high pressure side.

The design of the climate control system in a vehicle is based on the laws of nature, which mean that liquids evaporate when they are subjected to a temperature increase or a reduction in pressure and that heat is absorbed during this process.

If the hot vapor is then cooled again, the heat that has been absorbed is released and the gas reverts to liquid form. This process is repeated as many times as necessary, so that "cooling is produced" continually. This is the same type of process as used in refrigerators, for example.

Refrigerant

In order to remove heat from the passenger compartment a medium that has a lower evaporating temperature than air is used, because heat will always move from a hotter body to a cooler body. The medium that is used is refrigerant R134a.

R134a is a gaseous fluorocarbon. It is chlorine free and does not damage the ozone layer. However, R134a is still environmentally hazardous as it contributes to the greenhouse effect. It is therefore important that all service work is performed by trained personnel.

R134a retains its gaseous form at normal atmospheric pressure, and only condenses if it is cooled down to below -26 °C.

R134a has the following properties

1. can only be mixed with synthetic PAG oils (polyalkyline glycol) and not with mineral oils
2. does not affect metals
3. affects some types of plastic, so only special seals (O rings) that are intended for R134a should be used
4. is not explosive
5. is odorless
6. is not toxic in low doses
7. effectively absorbs moisture
8. is not flammable
9. is heavier than air in gaseous form.

Scheme 1112

The compressor is located at the front of the engine. The air conditioning compressor is installed on the auxiliaries bracket which is in turn installed on the cylinder block. There are no bushings between the air conditioning compressor, the auxiliaries bracket and the cylinder block. Direct mounting gives increased rigidity to the mounting. It minimizes the risk of noise.

The compressor is in the refrigerant circuit, located between the evaporator and the condenser.

The compressor has a fixed cylinder displacement.

Compressors with fixed displacement have two limits

1. off
2. on.

The air conditioning (A/C) compressor is controlled by an air conditioning (A/C) pressure sensor. The air conditioning (A/C) pressure sensor is positioned on the receiver drier. In vehicles with electronic climate control (ECC), the compressor is also controlled by the temperature after the evaporator.

The compressor is lubricated with specially developed refrigerant oil. This oil (synthetic PAG oil) is mixed with the refrigerant when the air conditioning system is in operation.

The compressor also has a relief valve, located on the rear section of the compressor. The relief valve functions as an additional safety device. The valve opens and releases refrigerant when the pressure in the system is too high (at approx. 3.5 MPa (35 bar)). The valve then shuts again when the pressure has returned to normal.

The compressor is mechanical and is driven by the vehicle engine. When the compressor is operating it "steals" 0.5-8 kW (0.7-11 bhp) from the engine. This may be noticed as slight jerks when driving as the compressor is engaged / disengaged.

The compressor is disengaged for 10 - 20 seconds under full acceleration.

The compressor is the component in the climate control system with the greatest mass. This means that the compressor takes the longest time to warm up. In climates with large differences in day and night temperatures this means that the compressor is often the coldest part of the system. All the refrigerant in the system therefore gathers in the compressor. The compressor cannot compress liquid which means that the pressure becomes very high and there is a risk that the safety valve will be activated when the system is switched on. The safety valve closes when the pressure falls but there is a slight release of refrigerant each time. When the liquid release occurs it also causes a loud noise and shaking.

To minimize the risk of liquid compression the compressor is engaged at the same time as the starter motor is operating. The starter motor has a lower engine speed (RPM) than the vehicle drive motor and the pressure build up in the compressor is not as high. The risk of the safety valve being deployed is minimized and any liquid refrigerant is driven from the compressor.

Scheme 1113

The compressor is mounted directly on the engine block and is driven by the engine crankshaft via the auxiliaries belt.

In the refrigerant circuit, the compressor is located between the evaporator and the condenser.

The compressor has variable displacement that is regulated by a replaceable solenoid, which is located on the underside of the compressor. The temperature sensor situated after the evaporator sends a signal to the Climate Control Module (CCM), which uses the signal to control the solenoid.

Compressors with variable displacement usually do not switch off during normal operation. The flow of refrigerant is continually adapted based on need. The compressor works between min. and max. displacement due to the following

1. the pistons are driven by a cam disc with a variable angle
2. the angle is determined by springs if the compressor is disengaged
3. if the compressor is engaged, the angle is determined by the pressure exerted on the top of the pistons (= intake pressure) and the bottom of the pistons (= pressure in the crankcase) during the intake phase
4. the pressure on the bottom of the pistons (= in the crankcase) is regulated by a solenoid that is controlled by the Climate Control Module (CCM).

If intake pressure is high, the compressor works to increase displacement.

1. The solenoid opens and lowers the pressure in the crankcase. The counterpressure on the back of the pistons then reduces and the cam disc angle increases.
2. The increased angle generates increased stroke, which causes a greater amount of refrigerant to be "sucked in" and a drop in intake pressure.

When intake pressure is low, the compressor works to reduce displacement.

1. The valve closes and pressure in the crankcase increases. The pressure is built up by refrigerant that is led from the outlet side to the crankcase via a calibrated duct. The counterpressure on the back of the pistons then increases and the cam disc angle decreases.
2. The decreased angle generated reduced stroke, which causes a smaller amount of refrigerant to be "sucked in" and an increase in intake pressure.

The compressor is also regulated by the A/C pressure sensor, which deactivates the system if pressure becomes too high.

The compressor is lubricated with specially developed refrigerant oil. This oil (synthetic PAG oil) is mixed with the refrigerant when the air conditioning system is in operation.

The compressor is the component of the climate control system with the largest mass. Thus, it takes the longest to warm up. In climates where the temperature varies greatly from night to day, it is often the compressor that is the system's coldest point each morning. Thus, all the refrigerant in the system makes its way to the compressor crankcase. Upon start, it takes 1-2 minutes for the refrigerant to evaporate. During this period, it may seem like the climate control system is not working.

Scheme 1114

1. Carrier disc
2. Shim discs
3. Spring ring
4. Pulley
5. Magnet coil.

The compressor is driven by the engine camshaft via the drive belt. As soon as the engine has started, the pulley (4) on the compressor drive shaft operates without hindrance.

Then the climate control system is switched on, the current passes through the magnetic coil (5), which is magnetized. This causes the carrier (1) on the compressor drive shaft to be pressed forward towards the pulley (4). The coupling is closed and the compressor rotates at the engine speed.

When the current to the magnetic coil is interrupted, the carrier disc (1) is released from the pulley (4) with the aid of return springs.

In order for the magnetic clutch to function correctly, the distance between the carrier disc (1) and the pulley (4) must be exactly correct. Shim discs (2) are therefore placed between them.

Scheme 1115

1. Diaphragm
2. Valve housing
3. Refrigerant in liquid form from the receiver drier
4. Refrigerant in liquid form to the evaporator
5. Refrigerant in gas form from the evaporator to the compressor.

The expansion valve is mounted on the intake and outlet pipes of the evaporator. In the refrigerant circuit, it is located on the high pressure side between the receiver drier and the evaporator.

The expansion valve is a pressure and temperature dependent flow regulator of the constriction type. At low cooling demand the amount of refrigerant is reduced by the valve closing. If the cooling demand increases the valve opens slightly to allow more refrigerant to the evaporator.

Systems with an expansion valve have a greater register than systems with a fixed choke because the amount of refrigerant can be better regulated to the cooling demand.

The expansion valve consists of a diaphragm (1) and a valve housing (2).

Cross section of the expansion valve

Scheme 1116

1. Valve inlet from receiver drier
2. Valve slide
3. Valve outlet to compressor
4. Temperature sensor
5. Diaphragm (filled with refrigerant)
6. Diaphragm
7. Valve inlet from evaporator
8. Valve outlet to evaporator
9. Ball valve
10. Spring.

Liquid refrigerant comes from the receiver drier and flows through the valve inlet (1). The ball valve (9) mists the refrigerant before the refrigerant flows on through the valve outlet (8) and into the evaporator.

The ball valve opening is controlled by the temperature and pressure in the refrigerant gas coming out of the evaporator.

If for example the temperature of the refrigerant gas, coming from the evaporator in the expansion valve intake (7), increases the temperature sensor (4) and increases the temperature of the refrigerant in the diaphragm head.

The refrigerant in the diaphragm head expands and compresses the ball valve in the valve seat downwards using the diaphragm (6) and a valve slide (2) so that the valve seat opens. The flow of the refrigerant to the evaporator increases. The evaporator is cooled and the temperature of the refrigerant gas is reduced.

The ball valve closes as soon as the temperature in the evaporator falls and therefore the temperature of the refrigerant in the diaphragm head also falls.

Scheme 1117

The evaporator is an air heated heat exchanger located in the distribution housing for the climate control system.

The surface of the evaporator is polyurethane coated to reduce bad odors. The polyurethane coating reduces the surface tension of the water and makes it easier for the water to run off.

The evaporator consists of pipe loops in which the refrigerant flows. The loops have flanges to increase the heat absorbing surface. The evaporator is inclined to make it easier for the condensation to run off. 10 - 11 liters of condensation are formed per hour. The condensation is led via a drainage house out of the distribution housing and down under the vehicle.

If one experiences bad odors when the vehicle is started, a workshop can activate a function which starts the blower fan a moment after the ignition key is moved to the 0 position. The fan blows the evaporator dry for a few minutes to prevent condensation and bad odors the next time the vehicle is used.

In the refrigerant circuit, the evaporator is located on the low pressure side between the expansion valve and the compressor.

In the evaporator there is a low pressure due to the expansion valve choke and the suction effect of the compressor. When the refrigerant enters the evaporator via the expansion valve, it expands and both its pressure and temperature lower.

When the warm air encounters the cold evaporator, the humidity condenses on the evaporator. The heat (energy) that is released during condensation is transferred to the refrigerant which evaporates. The temperature difference between the air and the refrigerant reduces. High humidity results in an increased need for cooling.

To obtain sufficient cooling capacity, the refrigerant's evaporation temperature must be considerably lower than the temperature desired in the passenger compartment. But to prevent the moisture that has condensed on the evaporator from freezing to ice, the air is not cooled below approximately +3 °C (at which stage the temperature of the refrigerant in the evaporator is approximately -3 °C).

There is a temperature sensor after the evaporator. The temperature sensor detects the temperature of the air that has passed through the evaporator. When the temperature is too low, the compressor is switched off. This is to prevent ice forming on the evaporator.

It is important that there is the correct amount of refrigerant in the climate control system.

1. Too much refrigerant in the evaporator causes the refrigerant to heat up, but it only evaporates partially. This means that a smaller amount of heat is absorbed from the air, which results in reduced cooling capacity
2. Too little refrigerant in the evaporator causes the refrigerant to evaporate and the vapor to overheat. This means that a smaller amount of heat is absorbed from the air, which results in reduced cooling capacity.

Scheme 1118

1. Intake line from the condenser
2. Outlet line to expansion valve
3. Drying element
4. Liquid refrigerant
5. Riser.

The receiver drier is located to the right of the condenser in the engine compartment. In the refrigerant circuit, it is located on the high pressure side between the condenser and the expansion valve.

Liquid refrigerant passes at high pressure from the condenser through the intake pipe (1) and into the receiver drier. A drier element (3) separates any moisture from the refrigerant and filters any contaminants.

The refrigerant passes onwards through the riser (5) to the outlet line (2) and on to the expansion valve.

If the cooling system has been open (unplugged) for 10 minutes, or has leaked for some time, so that moisture may have entered the system the receiver drier must be replaced.

The receiver drier can only absorb a limited amount of moisture. If the system contains more moisture than the receiver drier can handle it may lead to icing which blocks the expansion valve.

Scheme 1119

A linear pressure sensor is mounted directly on the receiver drier. The pressure sensor has an integrated measurement amplifier that generates an output voltage that is linear to the pressure.

The pressure sensor signal is used to control the following functions

1. the engine cooling fan (FC)
2. deactivation of the compressor when pressure is too high
3. deactivation of the compressor if the system has run dry of refrigerant.

Scheme 1120

The condenser is located in front of the engine radiator. The airflow and engine cooling fan (FC) blow air through the condenser. In the cooling system, the condenser is located on the high pressure side opposite the compressor and the receiver drier.

The condenser consists of pipe loops in which the refrigerant flows. The loops have flanges to increase the heat radiating surface.

When the refrigerant enters the condenser it is in gas form and has both high pressure and high temperature. In the condenser the hot refrigerant loses some of its heat to the surrounding cooler air. The refrigerant then condenses and changes into liquid form. The amount of heat given off = the amount of heat taken up in the evaporator + the amount of heat supplied by the compressor. In order to supply sufficient cooling capacity, the condensation temperature of the refrigerant must be greater than the temperature of the outside air.

Scheme 1121

1. The service valve for draining, vacuum pumping and filling with refrigerant
2. Service valve for draining and vacuum pumping.

One service valve is located on the low pressure side and one service valve is located on the high pressure side. The valves are different sizes. This is to avoid incorrect connection.

Hoses, pipes

All connections, apart from those for the expansion valve and condenser, have double O-rings as a seal. The connections for the expansion valve and condenser have single O-rings.

The O-rings are manufactured in a specially developed material (HNBR = hydrated nitrile rubber).

General

The air conditioning only functions at ambient temperatures above 0 °C. At temperatures lower than this, the pressure in the system is too low and the compressor is never engaged. This setting is made to prevent ice building up on the evaporator.

The air conditioning only functions when the engine is running. The air conditioning functions regardless of engine speed (RPM) and vehicle speed. The compressor is dependent on the engine speed, the higher the engine speed the more cooling that can be provided.

The blower fan must be operating before the climate control system can be engaged.

The air conditioning system has only two positions, off and on. If it is too cold in the passenger compartment, the temperature can be controlled with the normal heat and blower fan controls.

Air conditioning is based on the same principle as that used in refrigerators.

1. Compressor
2. Condenser
3. Engine cooling fan (FC)
4. Receiver drier
5. Expansion valve
6. Evaporator
7. Blower fan.

Explanation

A - High pressure, warm fluid

B - Low pressure, cold fluid

C - Low pressure, cold gas

D - High pressure, warm gas

Dark arrow - Warm air

Light arrow - Cold air

By allowing the refrigerant to circulate in the closed system and changing the pressure and volume it will change temperature and boil (evaporate). At the pressure found in the system, approximately 170 - 320 kPa (1.7 - 3.2 bar), the refrigerant boils at approximately 0 °C to +4 °C.

A condition of the refrigerant boiling is that the heat is accessible. This heat is taken from the air around the evaporator (6) where boiling occurs. When the heat is taken up by the refrigerant the surrounding air becomes cooler. It is this cooled air that is blown into the passenger compartment by the climate control system blower fan (7). The heat taken up by the refrigerant in the evaporator (6) is transported out to the engine compartment, where it is transferred to the air by the condenser (2). The condenser is cooled by the airflow and the engine cooling fan (FC) (3).

Compressor

The task of the compressor is to

1. draw gaseous refrigerant from the evaporator
2. compress the gas thereby increasing its pressure and temperature
3. expel the gas with high pressure and high temperature to the condenser.

The compressor takes in cold refrigerant gas from the evaporator on the intake side through the low pressure connection. In ideal conditions, the compressor compresses the refrigerant from approximately 200 kPa (2 bar) to between 1.2 MPa and 2.1 MPa (12 and 21 bar). During the process, the refrigerant heats up from 0 °C to between 70 °C and 110 °C. These pressure and temperature values apply when the system is operating under optimal conditions.

The relief valve, located on the rear section of the compressor, functions as an additional safety device. The valve opens and releases refrigerant when the pressure in the system is too high. The valve then shuts again when the pressure has returned to normal. The temperature of refrigerant gas can reach as high as 125 °C.

The compressor can only compress gases, as liquid would damage the compressor.

Scheme 1122

The expansion valve checks the refrigerant flow in the evaporator in relation to the temperature and pressure. The expansion valve gives an even temperature control because the amount of refrigerant is controlled as necessary.

Evaporator

The task of the evaporator is to cool and dry the air.

The refrigerant (the volume that is measured by the expansion valve) is sprayed into the evaporator. As soon as the refrigerant enters the cooling pipes, it evaporates due to the drop in pressure. During this process, heat is also extracted from the cooling pipes. The cooling pipes and the entire evaporator cool immediately. The refrigerant gas is then drawn out using the compressor.

The airflow is routed past the evaporator and is cooled and dried, and then forwarded to the passenger compartment via the air distribution ducts.

When the air entering the passenger compartment encounters the cold evaporator, the humidity in the air condenses on the evaporator. The water drains out under the vehicle via a drain hose. In the event of high humidity, this may be considerable quantities of water, which is often mistaken for a water leak from the engine for example.

Scheme 1123

The task of the receiver drier is to

1. function as a filter, taking up and binding moisture (water) found in the system
2. function as a storage container for leak detection agent.

The leak detection dye mixes with the oil. When a leak occurs, it is possible to locate the leak with UV light.

Condenser (air cooled heat exchanger)

The task of the condenser is to cool, so converting the hot, gaseous refrigerant to a liquid.

The compressor pumps in hot refrigerant gas under high pressure. The gas has a temperature of between 70 and 110°C in the intake on top of the condenser. When the hot gas flows through the pipe loop, it is cooled down and condensed. The heat that is removed from the gas during this process is transferred to the surrounding air. The engine cooling fan (FC), which is the same fan used by the engine cooling system, increases the airflow through the condenser. The air flow increases the transfer of heat from the refrigerant to the outside air.

The engine cooling fan (FC) is controlled by the linear pressure sensor (high-pressure and safety valve), located on the drier, via the engine control module (ECM) and via the control module for the engine cooling fan (FC). The engine cooling fan (FC) is also controlled by the engine coolant temperature (ECT).

Service valves

1. The service valve for draining, vacuum pumping and filling with refrigerant
2. Service valve for draining and vacuum pumping.

The service valves are used to

1. check the system through manometer connections
2. drain the system of refrigerant
3. vacuum pumping
4. filling with refrigerant, high-pressure side only (1).

Scheme 1124

1. Fan motor
2. Power unit
3. Housing rear climate control unit
4. Pipe rear climate control unit
5. Switch, fan speed
6. Air duct
7. Evaporator
8. Expansion valve
9. Drain hose.

The air conditioning unit is located inside the panel on the left hand side of the cargo compartment panels. The front and rear air conditioning refrigerant circuits are connected in parallel. The rear air conditioning is connected via a connector on the firewall.

The connection between the rear and front air conditioning units is via pipes and rubber hoses inside the passenger compartment. The fan (1) is operated using a control (5) placed on a panel at the rear of the passenger compartment.

The compressor, condenser and receiver drier are used together by the front and rear air conditioning units.

A T-connection is located on the high-pressure side in the engine compartment between the receiver drier and the expansion valve. A T-connection for refrigerant, with high pressure, from the front climate control unit to the rear climate control unit.

The refrigerant is sprayed into the rear evaporator using the rear expansion valve. Then the refrigerant is routed at low pressure back to the front air conditioning unit. The return routing is connected to the front cooling system using a T-connection located between the expansion valve and the compressor on the low pressure side of the engine compartment.

Scheme 1125

The air distribution system consists of

1. climate control system: blower fan damper filter recirculation throttle.
2. air ducts
3. vents.

Dampers control the outgoing air to

1. defroster
2. the dashboard vents
3. the floor outlets
4. 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

1. on the right-hand side of the left-hand drive vehicle
2. 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.

Scheme 1126

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.

1. Electronic climate control (ECC) has five damper motors
2. Manual climate control (MCC) has four damper motors.

There are eleven different dampers controlling the air flow of the climate control unit

1. 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
2. A floor vent for guiding the airflow to the front and rear of the floor
3. 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.
4. A ventilation shutter for guiding the airflow to the dashboard and B post
5. A fresh air damper for controlling the flow of external air into the climate control system
6. 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

1. fresh air enters through the fresh air intake in the climate control system under the plenum chamber
2. recirculated air from the passenger compartment.

Scheme 1127

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 above).

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.

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.

Scheme 1128

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.

Scheme 1129

The air distribution system distributes the air to the passenger compartment. It is used jointly by the heating system and the cooling system in the climate control system. The blower fan draws air into the system. Fresh air enters through the fresh air intake in the distribution housing under the plenum chamber.

The air passes through the filter and the evaporator, past the temperature damper and possibly though the heat exchanger, before being released into the passenger compartment through the vents.

The temperature of the air from all the air vents can be controlled separately for the right or left hand sides.

After circulating, the air disappears out of the passenger compartment though air vents at the rear of the vehicle.

The recirculation damper regulates the amount of incoming fresh air. The recirculation function makes it possible to prevent outside air from entering the passenger compartment, for example when the ambient air is contaminated with exhaust fumes, smoke, etc. This function can also be used for rapid heating or cooling of the passenger compartment.

If the recirculation function is used for an extended period, the air humidity in the passenger compartment increases. This is because of the humidity of the expelled breath of the passengers. This can result in mist on the windows. The recirculation function has a timer function to eliminate the risk of misting.

When the controls are in the Maximum cooling position all the air is taken from the passenger compartment. This produces more rapid cooling of the passenger compartment air.

In vehicles with an air quality system (AQS), the transition to recirculation takes place automatically if the level of contaminants in the outside air increases, when the system is in the AUTO mode.

Mist forms easily on the windows in cold, damp weather. The defroster vents release air towards the front and side windows. The air flow removes the mist that forms. As the air is dry, the airflow also prevents moist air from the passenger compartment reaching the glass, so countering misting. The air conditioning contributes significantly to these functions by dehumidifying the air at temperatures above 0°C.

The defroster function, for the electronic climate control system (ECC), automatically sets the climate control system for the best defrosting of windshields.

Evacuation valves

The evacuation valves are used to even out the pressure in the passenger compartment.

The rubber dampers in the evacuation valves open when the air pressure is slightly higher in the passenger compartment than outside. When the air pressure is the same on the inside and the outside, the rubber dampers close. This prevents water and air (odors, dust and exhausts fumes) from penetrating the passenger compartment.

Note. The evacuation valves must not be blocked, this will impair the function of the climate control system.

Air quality sensor, replacing

V70 2000

1. 2001 see «Replacing the air quality sensor»(ref-441131-S08950436012011121500000)
2. 2002- see «Air quality sensor»(ref-406987-S15351352342011070100000) .

Blower fan motor / power unit, replacing

V70 2000

1. See «Blower fan motor / power unit, replacing»(ref-406998-S31544559582011070100000) .

Blower fan motor passenger compartment temperature sensor, replacing

V70 2000

1. See «Blower fan motor passenger compartment temperature sensor, replacing»(ref-406998-S13492446422011070100000) .