Design

Design

Climate control unit







The climate control unit consists of the following components:
1. Heater element
2. Damper motor module (DMM), temperature left
3. Blower fan
4. Damper motor module (DMM), fresh air/recirculation
5. Power unit for blower fan motor
6. Particle filter
7. Damper motor module, ventilation and floor (also defroster for MCC)
8. Damper motor module (DMM), temperature right
9. Damper motor module (DMM), defroster (ECC).

Engine coolant constantly flows through the heater element. There is no valve to regulate the flow. The selected temperature is achieved using dampers for the right and left-hand sides of the car installed upstream and downstream of the heater element. These control the amount of air to be warmed. There are also dampers downstream of the heater element that guide the airflow to the correct air vent.

The climate control module provides infinitely variable electronic blower fan control. When AUTO mode (ECC only) is engaged the climate control module (CCM) adapts the blower fan speed to the setting of the controls and the vehicle speed. The blower fan can be set to run-on in order to reduce residual moisture in the evaporator (the function is not available for vehicle's with engine B8444S). A timer located in the central electronic module (CEM) controls the run-on time. 50 minutes after the engine has been switched off and the ignition has been turned to position 0 or I, the central electronic module (CEM) supplies power to the climate control module (CCM) and the blower fan is activated at full speed for 7 minutes. This run-on dries the evaporator and prevents bad odors.

This function is programmed at the factory, but can be deactivated in the event of customer complaints via programming of customer parameters. Programming is carried out via VIDA.

Damper motor module (DMM)







The damper motor module (DMM) consists of a control unit and a stepper motor. The different versions of the climate control system have up to 5 damper motor modules (DMM). These are for the different functions such as defroster and recirculation. The climate control module (CCM) communicates with the other damper motor modules (DMM) via two LIN buses, LIN bus 1 and LIN bus 2. The position of the damper motors on the LIN buses depends on whether the vehicle is left or right-hand drive.

When regulating the different dampers, the climate control module (CCM) transmits a request for a new damper position to the each damper motor module (DMM). The damper motor module (DMM) calculates and then regulates the required direction and number of steps required to obtain the requested position. The damper motor module (DMM) then transmits information to the climate control module (CCM) indicating the actual damper position and status.

When replacing the damper motor module (DMM), the new damper motor must be identified by the climate control module (CCM). This is carried out via VIDA. When replacing the damper motors, ensure that identification is carried out.

Each damper motor module (DMM) is powered via a relay in the central electronic module (CEM).

There are diagnostics for the damper motor module (DMM).

Cooling system (not B8444S)







The engine control module (ECM) controls the A/C compressor. When the air conditioning (A/C) compressor on the dashboard environment panel is activated, a request is transmitted via the control area network (CAN) to the engine control module (ECM) about the activation of the compressor. The engine control module (ECM) determines when the compressor must operate. If any of the following conditions are met the compressor is disconnected:
- high engine coolant temperature (ECT)
- wide open throttle (WOT)
- the engine has just been started
- overpressure in the air conditioning (A/C) system.

When the engine is started the engine control module (ECM) activates the air conditioning compressor for a short period even if the climate control module (CCM) has not transmitted a request for this. This is carried out for diagnosis. This check is carried out at all temperatures exceeding -6 degrees C.

The advantage in allowing the engine control module (ECM) to control the air conditioning compressor is that it can delay compressor activation somewhat, if the idling speed must be compensated for the extra load for example.

Cooling system (B8444S only)







The engine control module (ECM) controls the variable A/C compressor. When the A/C switch on the dashboard environment panel is activated, a request is transmitted via the control area network (CAN) to the engine control module (ECM) about the activation of the compressor. The engine control module (ECM) calculates the current to open the valve to control the variable A/C compressor. If any of the following conditions are met, the valve that activates the compressor is not opened:
- high engine coolant temperature (ECT)
- wide open throttle (WOT)
- the engine has just been started
- overpressure in the air conditioning (A/C) system.

When the engine is started the engine control module (ECM) activates the air conditioning compressor for a short period even if the climate control module (CCM) has not transmitted a request for this. This is carried out for diagnosis and maintenance at all temperatures exceeding 0 degree C.

For more information on the A/C compressor, see Design and function, engine control module (ECM)

Sun sensor (electronic climate control only)







See Design and Function, central electronic module (CEM).

Twilight sensor







See Design and Function, central electronic module (CEM).

Evaporator temperature sensor







The evaporator temperature sensor is installed on the heater. Its role is to inform the climate control module (CCM) of the temperature of the refrigerant. The climate control module (CCM) controls the request from the evaporator temperature sensor to activate the air conditioning compressor. The evaporator temperature sensor is directly connected to the climate control module (CCM).

There are diagnostics for the evaporator temperature sensor.

Air quality sensor (AQS) (ECC only, option)







The air quality sensor (AQS) is available as an option for ECC. The air quality sensor (AQS) is, together with a particle filter, part of a system which has the role of ensuring that the air in the passenger compartment is free of pollutants. The role of the air quality sensor (AQS) is to transmit a signal to the climate control module (CCM) if it detects increased concentrations of pollutants in the outside air. The air quality sensor (AQS) measures concentrations of COx and NOx.

The air quality sensor (AQS) compares the present values with previous ones and can calculate changes in pollutant concentrations.
The air quality sensor (AQS) communicates with the climate control module (CCM) via a LIN bus.

The signal from the air quality sensor (AQS) to the climate control module (CCM) has four steps, 0-3:

- off = no increase or reduction in pollutant level
- signal 1 = gradual increase in pollutant level
- signal 2 = medium increase in pollutant level
- signal 3 = rapid increase in pollutant level.

The climate control module (CCM) uses the signal to control the recirculation damper motor.

There are diagnostics for the air quality sensor (AQS).

Seat heaters







The system for the seat heaters consists of three different parts:
- a seat heating module (SHM) which controls the function for communicating with the climate control module (CCM)
- two heater pads
- a temperature sensor.

The seat heating module (SHM) is under the left and right-hand front seat. The heater pads are in the seat and backrest. The temperature sensor is in the seat.

The seat heating module (SHM) is directly connected to the heater pad and temperature sensor. The seat heating module (SHM) communicates with the climate control module (CCM) via a LIN bus.

There are diagnostics for the seat heating module (SHM).

Switches, dashboard environment panel, (lower section)







Across the lower section of the dashboard environment panel there is a 12V socket and space for a maximum of seven switches.

Each switch has its own identity. This is unique for the relevant function. The switches can therefore be positioned in any location on the dashboard environment panel, as long as they are installed in the off position. They do not have to be in any particular order. However, the identity of the installed switches must correspond with the car configuration file so that they can be activated. For further information regarding the car configuration file, see Design and Function, Downloading Software.

There are diagnostics for the switches.

Rear A/C (only XC90 with three rows of seats)







XC90 with three rows of seats is equipped with a rear A/C system. This consists of:
- power unit
- fan
- expansion valve
- blower fan switch.

The rear A/C system is controlled by a switch in the lower section of the dashboard environment panel. When the switch is activated, the climate control unit (CCM) transmits a signal to the rear electronic module (REM) via the controller area network (CAN). The rear electronic module (REM) supplies the power unit and the blower fan switch with voltage via a relay. The blower fan switch sends control voltage to the power unit based on the position of the control. The power unit converts the control voltage to supply voltage for the blower fan motor.

The rear A/C is directly connected to the front air conditioning via the high and low pressure pipes and hoses. The only way to control the cooling in the third row of seats is to control the fan speed using the rear fan switch.

The rear electronic module (REM) diagnoses the relay supply, otherwise the rear A/C cannot be diagnosed.