1998 JAGUAR X308 temperature sensor

Air Conditioning - Air Conditioning
Description and Operation
Introduction

Parts List
The climate control system features fully automatic control of temperature, blower speed (airflow) and air distribution to
maintain optimum comfort under most driving conditions.
Manual controls are provided to allow the operator to over-ride automatic operation.
System Features
ItemPart NumberDescription
1—Fascia panel with integral ducting
2—Heater / cooler assembly
3—A/CCM
4—Blower LH and RH
5—Plenum
6—Control panel
7—Solar sensor
8—Assembly valve - water
9—Assembly pump - water
10—Temperature sensor - external
11—Compressor
12—Pressure switch - 4 level
13—Motorized in-car aspirator (LHD shown)
14—Receiver drier
15—Condenser

Twin blower assemblies Center mounted evaporator, heater and air distribution unit Electric solenoid water valve controlled heating Electric water pump assembly Servo motor driven air distribution flaps Dedicated side glass defrost / demist vents External temperature sensor Motorised in-car aspirator Solar sensor
Electronic Control Panel
Liquid Crystal Display (LCD) Digital temperature display Manual fan speed level External temperature display Celsius / Fahrenheit selection Heated windshield switch (where fitted) Heated backlight switch Defrost switch Manual airflow distribution overrides (4) Access to self diagnostic system and error codes
Sensors
External ambient temperature sensor Motorized in-car aspirator Heater matrix temperature sensor Evaporator temperature sensor Solar sensor
These sensors feedback information to the Air Conditioning Control Module (A/CCM) which automatically adjusts air
temperature, airflow volume and distributi on from the air conditioning unit to maintain a stable passenger compartment
average temperature under changing weather conditions.
Major Components

Air Conditioning - Evaporator Core
Removal and Installation
Removal
1. Remove heater / cooler unit; refer to 82.25.21.

2. Remove air conditioning control module from heater / cooler
unit.
Slacken upper fixing.
Remove lower fixings.

3. Remove evaporator pipe firewall seal plate.
Remove screws.
Remove plate.

4. Disconnect heater matrix temperature sensor.
Detach heater matrix temperature sensor connector from
unit.
Disconnect connector.

5. Remove footwell servo motor from heater / cooler unit.
Disconnect connector.
Remove screws.
Remove motor complete with bracket.
6. Disconnect evaporator sensor connector.

Control Components - Control Components
Description and Operation
System Controls
The climate control system is controlled by : 1. 1. Manual input from the operator, via the center console located control panel.
2. 2. Automatically by means of the A/CCM.
Output is based upon input from the following devices:
Motorized In-car aspirator External air temperature sensor Coolant temperature sensor Heater 'air-off' (the temperature of the air leaving the matrix fins) temperature sensor Evaporator 'air-off' (the temperature of the air leaving the evaporator fins) temperature sensor Solar sensor Left hand blower recirculation / fresh air flap potentiometer Right hand blower recirculation / fresh air flap potentiometer Upper air distribution box (ADB) center and side face flap servomotor potentiometer ADB defrost flap servomotor potentiometer Air conditioning unit Foot flap servomotor potentiometer Air conditioning unit Cool Air Bypass flap servomotor potentiometer Thumbwheel controls on the facia vent assemblies which provide manu al adjustment of the airflow volume. Road and engine speed signals input to the A/CCM
Climate Control Panel
Communication between the control panel and the A/CCM is via a serial data communications link.

Switching the Climate Control system ON
The climate control system can be switched ON by pressing one of the following :
Ref #1 On / Off (resumes the system on in the previous settings).
Ref #10 A / C (resumes the system on in the previous settings).
Ref #11 AUTO (resumes the system on at the previous temperature setting).

Maximum Cooling (temperature setting LO)
Air Conditioning Control Module (A/CCM)
Location

The A/CCM is located on the right hand side of the air conditioning unit and controls all system functions.
The temperature within the passenger compartment is continually compared with the temperature selected on the control
panel LCD. The A/CCM receives data input signals and compares these with signal s from the system temperature sensors
and feedback devices. Based on this information the A/CCM adjusts the air outlet temperatur e, airflow and distribution from
the air conditioning system in to the passenger compartment.
Identification
ItemControlOverride Allowed
Water valveFully closed (energised)-
BlowerMaximumYes
Fresh / recircRecirculationYes
Air distributionFace (state lamp OFF)Yes
A/C systemONYes
Cool air by-passFully open-

Inputs / Outputs
1.1. Engine speed:
Input to the A/CCM from the ECM. Heated windshield and backli ght will be inhibited when engine speed < 50 RPM.
2. 2. Vehicle speed:
Input from the instru ment cluster. Blower speed control to minimise the effects of ram ai r. Road speed compensation is inhibited when maximum
cooling LO, or maximum heating HI, is selected; also inhi bited in defrost mode with airflow set to maximum.
Used to determine the frequency at which the exterior temperature display is updated.
3. 3. Coolant temperature (signal derived from ECM via instrument cluster):
Input from the heater matrix temperature sensor used to control water valve and thus vent temperatures. Used to monitor the temperature of coolant at the heater matrix to assist the control of air outlet temperature. Used to inhibit the blowers when heating is selected and the engine coolant temperature is below 30°C. Is used to provide progressive increase in blower speed up to 60°C. To inhibit the water valve and pump when the coolant temperature is = < 10°C
Sensors and Controls
Solar Sensor

The solar sensor is mounted on the top surface of the fascia between the defrost outlets.
The sensor is a photo-diode which is calibr ated to measure direct sunlight. It provides an output signal to the A/CCM which
automatically reduces air temperature an d increases fan speed (airflow volume) to compensate for solar heating.
Evaporator Sensor

This thermistor device changes electrical resistance as a result of temperature variations.
The sensor is positioned next to the evaporator fins and measures air temper ature after it has passed through the
evaporator. The sensor inputs a signal to the A/CCM which controls the compress or (see table) when the refrigeration
system is operating.
The sensor's connector is located on the LH side of the air conditioning unit, in front of the main power connector.
The A/CCM disengages the compressor clutch when the temperature of the air off the evaporator is 2° C or less. This is to
prevent the moisture which may collect between the cooling fins of the evaporator from freezing and thus restricting airflow.

Heater Matrix Temperature Sensor
Evaporator Temperature SignalCompressor State
3°CON - clutch engaged
2°COFF - clutch disengaged

The heater matrix temperature sensor is a thermistor which changes its electrical resistance in response to changes in air
temperature converting a temperature rating to an electrical signal.
The sensor connector is located on the RH SIDE of the air conditioning unit. The sensor bead is located inside the unit down-
stream from the heater matrix and measures the 'post-heater' air temperature, before the air is distribu ted to the cabin The
sensor provides a signal to the A/CCM which adjusts the duty ratio of the water valve to provide the required air
temperature from the heater.
Ambient Temperature Sensor
The sensor is a thermistor which changes its electrical resistance in response to changes in air temperature, converting a
temperature rating to an electrical signal.

The ambient temperature sensor measures exterior air temper ature and is mounted on the crossbeam, in front of the
condenser on the LH side.

The signal from the ambient sensor allo ws the A/CCM to compensate for the ambient conditions and to display the
information on the control panel - updated every four (4) seconds.
Sensor response is 'damped' by the A/CCM and ther efore does not appear to react to temperature chan
ges as quickly as the