Automatic A/c-Heater Systems: Other Jaguar S-type I

DUAL AUTOMATIC TEMPERATURE CONTROL MODULE/PANEL

The Dual Automatic Temperature Control (DATC) electrical control module is a single module located in the center stack of vehicle. It is a microprocessor-based control consisting of a bezel assembly (including all control buttons and switches), a main control board and a housing for unit. DATC module/panel provides driver interface controls. see scheme 1 Operating any DATC controls activates a chime. DATC automatically maintains a selected temperature for interior of vehicle. DATC will try to provide both the driver and passenger with their selected temperature for comfort. Fan controls and air distribution are not controlled individually.

DATC module monitors evaporator discharge temperature sensor and communicates with PCM to control clutch cycling. DATC also monitors ambient air temperature and disables A/C operation when ambient air temperature is less than 32°F (0°C).

BLOWER MOTOR SPEED CONTROL

Variable blower speed is controlled by a Variable Blower Control (VBC) module with an integral high blower relay. There are 7 preset blower speeds that can be manually selected from control panel or selected by the DATC in automatic mode. In automatic mode, blower speed is based on desired in-vehicle temperature, monitored ambient temperature, discharge air temperatures, in-vehicle temperature and sun load levels. Blower speed can be affected while in automatic mode by cold ambient temperatures. DATC system implements a Cold Engine Lockout (CELO) feature with blower motor. When vehicle interior is cold, DATC system will operate in low blower/defrost mode until engine coolant temperature reaches a required value. When engine coolant has warmed up, blower motor will operate according to automatic mode commands.

At high vehicle speeds (monitored by SCP Vehicle speed status message), DATC system may adjust blower motor speed to maintain a constant airflow. This may be necessary in situations where ram air effect at high speed changes airflow into vehicle interior.

If vehicle is equipped with a cellular phone, DATC module may lower blower motor speed to reduce ambient noise when phone is in use. Cellular phone status is monitored by the SCP cellular phone ON or OFF message.

Heater Auxiliary Coolant Pump

On vehicles equipped with 4.0L engine, an electric coolant pump circulates coolant through heater system to provide increased coolant flow during low engine speed operation. The pump is also used to circulate coolant after the engine is turned off under certain conditions.

Heater Dual Coolant Control Valve

The heater core is separated into 2 sections. Air passing through one section is directed to the driver side, while air passing through the other section is directed to the passenger side. There are 2 separate heater core inlet ports and a common outlet port. Heater dual coolant valve regulates flow of engine coolant to each half of heater core. There are 2 electric solenoids, which are individually actuated by DATC module. The control valve contains 5 ports

1. An inlet port for coolant from engine.
2. An outlet port for coolant to driver side of heater core.
3. An outlet port for coolant to passenger side of heater core.
4. A return port for common coolant return from heater core.
5. An outlet port for coolant return to engine.

A/C REFRIGERANT PRESSURE TRANSDUCER/CUT-OFF SWITCH

A/C refrigerant pressure transducer monitors compressor discharge pressure. PCM will interrupt A/C compressor operation if A/C pressure transducer indicates high system discharge pressures. Pressure transducer is also used to sense no or low charge conditions. If system pressure is less than a predetermined value for a specific ambient air temperature, PCM will not allow compressor clutch to engage. Refrigerant pressure transducer also signals PCM for control of cooling fan speed.

When compressor discharge pressure increases to approximately 420 psi (29.5 kg/cm 2 ), PCM will disengage A/C compressor clutch. When discharge pressure decreases to approximately 250 psi (17.6 kg/cm 2 ) PCM will enable A/C compressor clutch.

A/C refrigerant pressure transducer is mounted on a Schrader-type valve fitting on A/C compressor-to-condenser discharge line. It is not necessary to discharge refrigerant system to remove A/C pressure transducer.

A/C COMPRESSOR PRESSURE RELIEF VALVE

A/C compressor pressure relief valve is incorporated in compressor A/C manifold and tube. Pressure relief valve opens when refrigerant system discharge pressures are excessive to prevent damage to compressor and other system components. Pressure relief valve closes to avoid total refrigerant loss after excessive pressure has been relieved.

A/C SYSTEM PERFORMANCE

Information is not available from manufacturer.

PIN VOLTAGE TESTS

Note. The values listed are approximately those that can be expected at the DATC module connector terminals with all circuit connections clean and tight, and all components connected and installed correctly. Active indicates that a load is applied or a switch is ON. Inactive indicates that a load is not applied or a switch is OFF.

Note. A/C system related tests should be performed with an ambient temperature of at least 50°F (10°C). Operate A/C system and verify proper operation. Visually inspect components for obvious signs of mechanical damage (proper refrigerant level, fuses, compressor and/or clutch, or drive belt damage) or electrical damage (faulty or damaged circuits, heater control flaps, blower motor, damaged or loose connectors, A/C compressor or cooling fan). Repair obvious cause for an observed or reported concern if possible. If concern is not visually evident, verify symptom and refer to Jaguar Portable Diagnostic Unit (PDU).

Pin voltage tables are supplied to reduce diagnostic time. See DATC MODULE TERMINAL ASSIGNMENTS (FC27, 26-PIN CONNECTOR) and DATC MODULE TERMINAL ASSIGNMENTS (FC28, 22-PIN CONNECTOR). Checking pin voltages at A/C Dual Automatic Temperature Control (DATC) determines whether it is receiving and transmitting proper voltage signals. (Scheme 6) Charts may also help determine if control unit wiring harness has a short or open circuit. See WIRING DIAGRAMS.

Scheme 6

DATC MODULE TERMINAL ASSIGNMENTS (FC27, 26-PIN CONNECTOR)

DATC MODULE TERMINAL ASSIGNMENTS (FC28, 22-PIN CONNECTOR)

EVAPORATOR CORE & HEATER CORE

Note. If a heater core leak is suspected, heater core must be leak tested in the vehicle before removal.