11.3 - Climate Control Test and Diagnosis ( ,  )

The climate control system is significantly different from earlier XJ40 models in that all flaps and valves are electrically operated, with no reliance on engine vacuum. The system is of the 'constant air flow' type, meaning that fan speed is adjusted based on road speed to maintain the desired flow rate.

The system can be put through a self-test procedure as follows:

Warm the engine then switch off. Press both 'Auto' and 'Recirc' buttons and hold whilst restarting the engine.

All the panel LED's and LCD display will flash. Any areas failing to flash suggest a problem with the bulb, display or function in that area.

Press 'Auto'. If the display is zero, then no error codes are stored. Any other number is an error code. Use 'demist' to cycle through up to five stored codes. Press 'demist' and 'heated rear window' to clear a displayed code. Code 23 indicates low refrigerant pressure.

Press 'Recirc' to enter diagnostic mode. Repeatedly pressing 'Face' will step through the 8 different combinations of vent actuation and you will be able to hear and feel vents and fan operating.

Pressing 'Off' will restore the unit to normal operation with the default settings.

List of control codes:

0 - Normal Operation - No fault codes present, wait 30 seconds for system
self-check.
11 - Motorized In-car Aspirator (sensor element)Open / short circuit. Panel
fault codes are not stored for blown aspirator failure of motor.
12 - Ambient Temperature SensorOpen / short circuits.
13 - Evaporator Temperature SensorOpen / short circuits.
14 - Engine Coolant Temperature InputInstrument pack output.
15 - Heater Matrix Temperature SensorOpen / short circuits.
21 - Solar SensorOpen / short circuits.
22 - Compressor Lock SignalOpen / short circuits. Low gas charge, low
compressor oil, loose belt.
23 - Refrigerant Pressure SwitchOpen / short circuits. Low gas charge*.
24 - Differential PotentiometerOpen / short circuits.
31 - LH Fresh / Recirc. PotentiometerOpen / short circuit in pot.
feed. In certain circumstances, the motor can over-travel and log further
faults. Cycling the ignition two or three times can cure this.
32 - RH Fresh / Recirc. Potentiometer
33 - Cool Air Bypass Potentiometer
34 - Defrost Potentiometer
35 - Centre Vent Potentiometer
36 - Foot Potentiometer
41 - LH Fresh / Recirc. MotorCheck for short / open circuits in motor drive
lines. Motor flap sticking / jammed.
42 - RH Fresh / Recirc. Motor
43 - Cool Air Bypass Motor
44 - Defrost Motor
45 - Centre Vent Motor
46 - Foot Motor

Other symptoms that don't generate codes

No heat - Airlock in system. Water pump inoperative. Water valve stuck
closed. Faulty engine coolant thermostat.
One vent failing to open or close - Broken linkage.
Poor airflow - Blower motors - incorrect operation (eg fuses blown).