Description - 2

Description - 2 Con't


General


Low Line Control Panel







The switches on the low line control panel have the following functions:
- Windscreen Heater Switch: Enabled only with the engine running. Pressing the switch energises the windscreen heater and the windscreen wiper parking area heater for a set time period until the switch is pressed again or until the engine stops, whichever occurs first. A LED above the switch is illuminated while the heaters are on.
- LH and RH Seat Heater Switches: Activates the heater elements in the seat cushion and seat back at one of two heat levels. The first press of the switch energises the heater elements at the higher heat setting and illuminates two LED in the switch. A second press of the switch sets the heater elements to the lower heat setting and extinguishes one of the LED's. A further press of the switch de-energises the heater elements and extinguishes the second LED. The seat heaters remain on until selected off or the ignition is switched off.
- Temperature Switch: Adjusts the passenger compartment nominal temperature setting between 16 and 28 °C (60 and 84 °F). The temperature range is engraved on the switch surround (°F for NAS, °C for rest of world). A pointer on the switch indicates the selected temperature. In the minimum and maximum temperature positions, the temperature is set to maximum cooling or maximum heating respectively.
- Blower Switch: For manual adjustment of blower speed. Up to seven LED's in the switch surround illuminate to indicate the selected blower speed.
- Distribution Control Knob: For manual adjustment of air distribution. Includes AUTO setting where distribution flaps are set to a nominal comfort position.
- A/C Switch: Activates the A/C compressor. Allows the A/C compressor to be selected off for economy operation. A LED above the switch is illuminated when the A/C compressor is selected on.
- Recirculation Switch: For manual selection of fresh or recirculated air. A LED above the switch is illuminated when recirculated air is selected.
- Rear Window Heater Switch: Enabled only with the engine running. Pressing the switch energises the rear window heater for a set time period until the switch is pressed again or until the engine stops whichever occurs first. A LED above the switch is illuminated while the heater is on.

High Line Control Panel







The switches on the high line control panel have the following functions:
- Windscreen Heater Switch: Energises the windscreen heater and the windscreen wiper parking area heater for a set time period, until the switch is pressed again or until the engine stops, whichever occurs first. A LED above the switch is illuminated while the heaters are on.
- LH and RH Seat Heater Switches: Activates the heater elements in the seat cushion and seat back at one of two heat levels. The first press of the switch energises the heater elements at the higher heat setting and illuminates two LED in the switch. A second press of the switch sets the heater elements to the lower heat setting and extinguishes one of the LED's. A further press of the switch de-energises the heater elements and extinguishes the second LED. The seat heaters remain on until selected off or the ignition is switched off.
- LH and RH Temperature Switches: Adjusts the nominal temperature settings of the LH and RH sides of the passenger compartment between 16 and 28 °C (60 and 84 °F). The temperature range is engraved on the switch surrounds. A pointer on each switch indicates the selected temperature. In the minimum and maximum temperature positions, the system operates at maximum cooling or maximum heating respectively.
- Automatic Mode Switch: Activates the automatic modes for air volume and distribution and also activates the compressor. Separate LED's in the automatic mode switch illuminate when the blower and the distribution control flaps are in automatic mode. Manually selecting the blower speed or a distribution switch extinguishes the related LED.
- Blower Switch: For manual adjustment of blower speed. Up to seven LED's in the switch surround illuminate to indicate the selected blower speed.
- A/C Switch: Controls activation of the A/C compressor. Allows the A/C compressor to be selected off for economy operation. A LED above the switch is illuminated when the A/C compressor is selected on.
- Recirculation Switch: For manual or automatic selection of fresh or recirculated air. Two LED's above the switch illuminate to indicate the mode and position of the recirculation flaps. The first press of the switch sets the recirculation flaps to automatic mode and illuminates the LH LED. A second press of the switch manually sets the recirculation flaps to the recirculation position, extinguishes the LH LED and illuminates the RH LED. A further press of the switch manually sets the recirculation flaps to the fresh air position and extinguishes the RH LED.
- Maximum A/C Switch: For selection of maximum A/C when the ignition is on or rest heating when the ignition is off. A LED above the switch is illuminated when maximum cooling or rest heating is selected.
- Distribution Switches (Windscreen, Face and Footwell): For manual selection of air distribution in any combination of windscreen, face and footwell outlets. A LED above each switch illuminates when a selection is made.
- Defrost Programme Switch: Activates a programme that automatically selects the windscreen heater on, activates the compressor and changes the system settings to direct dry heat to the windscreen. A LED above the switch is illuminated while the defrost programme is active.
- Rear Window Heater Switch: Enabled only with the engine running. Pressing the switch energises the rear window heater for a set time period, until the switch is pressed again or until the engine stops, whichever occurs first. A LED above the switch is illuminated while the heater is on.

Inputs and Outputs
Five electrical connectors provide the interface between the ATC ECU and the vehicle/heater assembly wiring. Both the low and high line systems receive ambient temperature, engine coolant temperature, engine speed and vehicle speed inputs in K bus messages from the instrument packs. If the K bus messages are missing or faulty, the ATC ECU adopts the following default values:
- Ambient temperature 0 °C (32 °F)
- Engine coolant temperature = 80 °F (176 °F)
- Engine speed = 800 rev/min
- Vehicle speed = zero

If a fault develops in the input from the temperature selector switch on the control panel, the ATC ECU adopts a default value of 24 °C (75 °F).

Sensors
Both the low and the high line systems incorporate:
- An in-car temperature sensor
- A refrigerant pressure sensor
- An evaporator temperature sensor
- A heater matrix temperature sensor

The high line system also incorporates:
- A second heater matrix temperature sensor
- A sunlight sensor
- A pollution sensor

In-car Temperature Sensor
The in-car temperature sensor is an encapsulated Negative Temperature Coefficient (NTC) thermistor that provides the ATC ECU with an input of passenger compartment air temperature. The in-car temperature sensor is installed behind a grille in the ATC ECU control panel. An electric fan in the ATC ECU runs continuously, while the ignition is on, to draw air through the grille and across the in-car temperature sensor.

The ATC ECU uses the signal from the in-car temperature sensor for control of the coolant temperature valve(s), blower speed and air distribution.

The signal voltage from the in-car temperature sensor is between 0 and 5 V. The ATC ECU monitors the signal voltage and defaults to a temperature of 20 °C (68 °F) if it goes out of the range 0.573 - 4.882 V:
- If the signal voltage is less than 0.573 V, the ATC ECU assumes there is a short circuit to ground
- If the signal voltage is more than 4.882 V, the ATC ECU assumes there is an open circuit or a short circuit to battery.

Refrigerant Pressure Sensor
The refrigerant pressure sensor provides the ATC ECU with a pressure input from the high pressure side of the refrigerant system. The refrigerant pressure sensor is located in the refrigerant line between the condenser and the thermostatic expansion valve.

The ATC ECU supplies a 5 V reference voltage to the refrigerant pressure sensor and receives a return signal voltage between 0 and 5 V, related to system pressure.

The ATC ECU uses the signal from the refrigerant pressure sensor to protect the system from extremes of pressure and to calculate compressor load on the engine for idle speed control. The ATC ECU also transfers the pressure value to the Engine Control Module (ECM), via the K bus, instrument pack and CAN bus, for use in controlling the speed of the engine cooling fan.

To protect the system from extremes of pressure, the ATC ECU disengages the compressor clutch if the pressure:
- Decreases to 1.9 + 0.2 bar (27.5 + 3 lbf/sq.in): the ATC ECU engages the compressor clutch again when pressure increases to 2.8 + 0.2 bar (40.5 + 3 lbf/sq.in)
- Increases to 33+ 1 bar (479+ 14.5 lbf/sq.in): the ATC ECU engages the compressor clutch again when pressure decreases to 23.5 1 1 bar (341 1 14.5 lbf/sq.in)

Evaporator Temperature Sensor
The evaporator temperature sensor is a NTC thermistor that provides the ATC ECU with a temperature signal from the air outlet side of the evaporator. The evaporator temperature sensor is installed in the RH side of the heater assembly casing and extends into the core of the evaporator.

The ATC ECU uses the input from the evaporator temperature sensor to control the engagement and disengagement of the compressor clutch to prevent the formation of ice on the evaporator.

The signal voltage from the evaporator temperature sensor is between 0 and 5 V. The ATC ECU monitors the signal voltage and defaults to a temperature of 0 "C"(32 °F) if it goes out of the range 0.157-4.784 V:
- If the signal voltage is less than 0.157 V the ATC ECU assumes there is a short circuit to ground
- If the signal voltage is more than 4.784 V, the ATC ECU assumes there is an open circuit or a short circuit to battery

Heater Matrix Temperature Sensor
The heater matrix temperature sensor is a NTC thermistor that provides the ATC ECU with a temperature signal from the air outlet side of the heater matrix. On low line Systems, a single sensor is installed in the rear of the heater assembly casing to the right of the centre-line. On high line systems two sensors are installed one each side of the centre-line.

The ATC ECU uses the input from the heater matrix temperature sensor(s) to control the operation of the coolant valve(s).
The signal voltage from each heater matrix temperature sensor is between 0 and 5 V. The ATC ECU monitors the signal voltage and defaults to a temperature of 55 °C (131 °F) if it goes out of the range 0.173-4.890 V:
- If the signal voltage is less than 0.173 V the ATC ECU assumes there is a short circuit to ground
- If the signal voltage is more than 4.890 V, the ATC ECU assumes there is an open circuit or a short circuit to battery

Sunlight Sensor
The sunlight sensor consists of two photoelectric cells that provide the ATC ECU with inputs of light intensity one as sensed coming from the left of the vehicle and one as sensed coming from the right. The inputs are a measure of the solar heating effect on vehicle occupants and used by the ATC ECU to adjust blower speed, temperature and distribution to improve comfort. The sensor is installed in the centre of the fascia upper surface.

If one of the photoelectric cells is faulty, the output from the other photoelectric cell is used for both sides of the vehicle. If both photoelectric cells are faulty the ATC ECU uses a default value of zero.

Pollution Sensor
The pollution sensor allows the ATC ECU to monitor the ambient air for the level of hydrocarbons and oxidized gases such as nitrous oxides, sulphur oxides and carbon monoxide. The pollution sensor is installed at the rear of the radiator, on the upper RH side of the viscous fan housing.

The ATC ECU outputs a battery power supply to heat the pollution sensor to operating temperature and a 5 V reference voltage for the signal. The signal voltage from the pollution sensor is between 0 and 5 V.

If there is a fault with the pollution sensor, the ATC ECU disables automatic closing of the recirculate on flaps on detection of pollutants.

Auxiliary Coolant Pump
The auxiliary coolant pump is an electric pump that ensures there is a satisfactory flow rate through the heater matrix at low engine speeds. The auxiliary coolant pump is installed in the engine compartment, in a rubber mounting attached to the side of the LH suspension turret. Operation of the auxiliary coolant pump is controlled by a power supply from the ATC ECU.

Coolant Valve
The coolant valve controls the coolant flow to the heater matrix. A single coolant valve controls the coolant flow to both sides of the heater matrix on low line systems. On high line Systems, separate coolant valves control the coolant flow to each side of the heater matrix. The coolant valves are installed in the engine compartment on a bracket attached to the side of the LH suspension turret.

Each coolant valve is a normally open solenoid valve controlled by a Pulse Width Modulated (PWM) signal from the ATC ECU. The ATC ECU changes the length of time the coolant valve is open each duty cycle between 0 second (valve closed) and 3.6 seconds (valve held open). On the high line system the PWM signals to the two valves are phase offset by 1.8 seconds to reduce coolant flow fluctuations.

FBH System
The system consists of a FBH unit, a FBH fuel pump and a changeover valve. On vehicles with the remote operation feature, the system also includes a FBH receiver and a remote handset.

Fuel for the FBH system is taken from the vehicle fuel tank, through a line attached to the fuel tank's fuel pump unit, and supplied via the FBH fuel pump to the FBH unit. In the FBH unit the fuel delivered by the FBH fuel pump is burned and the resultant heat output is used to heat the engine coolant. The changeover valve isolates the heater coolant circuit from the engine coolant circuit

An ECU integrated into the FBH unit controls the operation of the FBH unit and the FBH fuel pump. The ATC ECU controls the changeover valve. System operation is initiated by:
- The instrument pack, via the ATC ECU, using I and K bus messages for parked heating selections made on the Multi Information Display (MID) or Multi-Function Display (MFD)
- The remote handset, via the TV antenna, TV amplifier and the FBH receiver, using radio and hardwired signals, for instant activation of parked heating
- The ATC ECU, using K bus messages, for additional heating while the engine is running

FBH Fuel Pump
The FBH fuel pump regulates the fuel supply to the FBH unit. The FBH fuel pump is installed below the RH side of the fuel tank in a rubber mounting attached to the rear subframe. The pump is a self priming solenoid operated plunger pump. The ECU in the FBH unit outputs a pulse width modulated signal to control the operation of the pump. When the pump is de-energised, it provides a positive shut-off of the fuel supply to the FBH unit.

Sectioned View of FBH Fuel Pump







The solenoid coil of the FBH fuel pump is installed around a housing which contains a plunger and piston. The piston locates in a bush, and a spring is installed on the piston between the bush and the plunger. A filter insert and a fuel line connector are installed in the inlet end of the housing. A non return valve and a fuel line connector are installed in the fuel outlet end of the housing.

While the solenoid coil is de-energised the spring holds the piston and plunger in the 'closed' position at the inlet end of the housing. An 'O' ring seal on the plunger provides a fuel tight seal between the plunger and the filter insert, preventing any flow through the pump. When the solenoid coil is energised, the piston and plunger move towards the outlet end of the housing, until the plunger contacts the bush; fuel is then drawn in through the inlet connection and filter. The initial movement of the piston also closes transverse drillings in the bush and isolates the pumping chamber at the outlet end of the housing. Subsequent movement of the piston then forces fuel from the pumping chamber through the non return valve and into the line to the FBH unit. When the solenoid de-energises, the spring moves the piston and plunger back towards the closed position. As the piston and plunger move towards the closed position, fuel flows past the plunger and through the annular gaps and transverse holes in the bush to replenish the pumping chamber.

FBH Unit
The FBH unit is installed in the passenger side rear of the engine compartment below the battery. It is connected in series with the coolant supply to the heater assembly. Two electrical connectors on the FBH unit connect it to the vehicle wiring.

FBH Unit Components







Sectioned View of FBH Unit







The FBH Unit consists of:
- A circulation pump
- A combustion air fan
- A burner housing
- An ECU/heat exchanger
- An air inlet hose
- An exhaust pipe
- An air inlet filter


Circulation Pump: The circulation pump is installed at the coolant inlet to the FBH unit to assist the coolant flow through the FBH unit and the heater assembly. The pump runs continuously while the FBH unit is in standby or active operating modes. While the FBH Unit is inactive coolant flow is reliant on the engine coolant pump and the auxiliary coolant pump.

Combustion Air Fan: The combustion air fan regulates the flow of air into the unit to support combustion of the fuel supplied by the FBH pump and to purge and cool the FBH unit. A canister type filter is included in the air inlet supply line to prevent particulates entering and contaminating the FBH unit.

Burner Housing: The burner housing contains the burner insert and also incorporates connections for the exhaust pipe, the coolant inlet from the circulation pump and the coolant outlet to the heater assembly. The exhaust pipe directs exhaust combustion gases to atmosphere through a pipe below the FBH unit.

The burner insert incorporates the fuel combustion chamber, an evaporator and a glow plug/flame sensor. Fuel from the FBH fuel pump is supplied to the evaporator where it evaporates and enters the combustion chamber to mix with air from the combustion air fan. The glow plug/flame sensor provides the ignition source of the fuel:air mixture and, once combustion is established, monitors the flame.

ECU/Heat Exchanger: The ECU controls and monitors operation of the FBH system. Ventilation of the ECU is provided by an internal flow of air from the combustion air fan. The heat exchanger transfers heat generated by combustion to the coolant. A sensor in the heat exchanger provides the ECU with an input of heat exchanger casing temperature, which the ECU relates to coolant temperature and uses to control system operation. The temperature settings in the ECU are calibrated to compensate for the difference between coolant temperature and the heat exchanger casing temperature detected by the sensor. Typically, as the coolant temperature increases, the coolant will be approximately 7 °C (12.6 °F) hotter than the temperature detected by the sensor: as the coolant temperature decreases, the coolant will be approximately 2 °(3.6 F) cooler than the temperature detected by the sensor.

Changeover Valve
The changeover valve is a normally open solenoid valve installed between the supply and return sides of the heater coolant circuit. The changeover valve is located in the engine compartment on the engine bulkhead. When de-energised, the changeover valve connects the heater coolant circuit to the engine coolant circuit. When energised, the changeover valve isolates the heater coolant circuit from the engine coolant circuit.

The changeover valve is controlled by a power feed from the ATC ECU.

FBH Receiver
The FBH receiver translates the FBH request radio signals, relayed from the antenna receiver, into a voltage output to the FBH unit. When a request for parked heating is received, the FBH receiver outputs a battery power feed to the FBH unit. When a request to switch off parked heating is received, the FBH receiver disconnects the power feed.

The FBH receiver has a permanent power feed from the vehicle battery and is connected to the antenna receiver by a coaxial cable.

Remote Handset
The remote handset allows parked heating to be remotely controlled up to 300 m (985 ft) from the vehicle. On/Off buttons activate and de-activate parked heating and a green LED flashes to indicate when parked heating is active. An extendable antenna is installed in the top of the remote handset. The remote handset is powered by two serviceable 1.5 V batteries, which can be accessed by sliding open the rear panel.