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 calibrated to measure direct sunlight. It provides an output signal to the A/CCM which automatically reduces air temperature and 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 temperature after it has passed through the evaporator. The sensor inputs a signal to the A/CCM which controls the compressor (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.

Evaporator Temperature Signal Compressor State
3 °C ON - clutch engaged
2 ° OFF - clutch disengaged

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







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 distributed 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 temperature and is mounted on the crossbeam, in front of the condenser on the LH side.







The signal from the ambient sensor allows 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 therefore does not appear to react to temperature changes as quickly as the other sensors. This feature prevents the effects of sudden changes in air outlet temperatures due to factors such as:
- Recirculating air from the engine cooling pack at low vehicle speeds
- Sudden changes in ambient temperature
- The effects of water splash

Motorized In-car Aspirator.







An intake grille (mounted on the fascia, outboard of the steering column and below the EOD vent) houses the aspirator thermister. The remotely mounted motor/fan assembly draws cabin air through the grille and thus over the thermistor; a flexible hose connects both components.

The electrical resistance of the thermistor changes in response to variations in air temperature, this change being converted into an electrical signal. The A/CCM uses this signal to adjust the temperature, airflow and air distribution from the air conditioning unit.

Coolant Temperature Signal.
This signal is supplied to the A/CCM from the instrument cluster, the input being required to:
- Provide blower inhibit control ,to avoid the system in heating mode delivering cold air when the coolant temperature is below 35°C unless DEFROST is selected.
- To progressively increase the fan speed up to maximum blower speed during warm up control.
- To assist in the control of the outlet temperature.
- To avoid possible pump or valve damage caused by ice particles in the coolant.

Compressor ON Signal.
This signal monitors the compressor relay to confirm the compressor operating state and so provide relevant fault information.

Servo Motor Control.
Flap position, which directs the flow of air through the system, is controlled by servo motors; these may be driven in either a clockwise or anti-clockwise direction by signals from the A/CCM. Motor, thus flap position, is monitored via a feedback potentiometer which is situated within the motor housing.

Servo motors control the following flaps:
- RH and LH Air Intake (Fresh/Recirc)
- Center Vent
- Defrost
- Foot
- Cool Air Bypass

Blower Motor Control.
The A/CCM controls the speed of two blower motors which deliver airflow to the air conditioning unit. The blower motors are regulated by power transistor modules which provide a linear variation of blower speed.

Filter Compensation
Where particle filters are fitted as 'after market' items the A/CCM program must be changed to allow higher AUTO blower speeds; this compensates for the slight loss of air flow. Access to the program is by PDU.

Vehicles with filters fitted OEM will have this facility enabled by Jaguars Cars Ltd.

Relationship Manual Control Blower Speed/Voltage


NOTE: Blower motors are inhibited when the engine coolant temperature is below 35 °C and heating is demanded, unless DEFROST/DEMIST is selected.