In reply to a message from XJ6FangXK40 sent Fri 20 Mar 2009:
Yes, the aircon controls can be confusing / amusing!
Here’s something I drew up for the '91 model which I have
modified 9enough I hope) to reflect the very similar
controls on your earlier car:-
FAN (BLOWERS) CONTROL ROTARY SWITCH (on left of control panel)
OFF - The system is not operational. Power is off, but a
signal is sent to the ECU to ensure that the recirculation
(blower intake) flaps are closed to prevent outside air from
entering the car.
LOW - The ECU maintains blower speed within a range of low
speeds, depending on the temperature requirement.
MED - The ECU controls the full range of blower speeds,
depending on the temperature requirement.
HIGH - The blowers run at high speed only.
DEF - The blowers run at high speed - full air flow at �full
heat� is directed to the windshield.
TEMPERATURE CONTROL ROTARY SELECTOR (on right of control panel)
MODE BUTTON
AUTO - The system is under ECU control and automatically
maintains the selected IN-CAR temperature and humidity level.
MAN - The system sensors are overridden and the selected
temperature is provided at the VENT outlets.
[Note the differentiation between �In-car temperature� and
�Vent outlet temperature�]
SCREEN BUTTON [‘AIR’ button on your car]
When illuminated - Windshield demisting is provided but
with NO change to air temperature. The demist vents are
vacuum controlled and are normally held closed until ‘AIR’
or ‘Defrost’ is selected.
HUMIDITY BUTTONS
ALL OFF (maximum dehumidification) - The evaporator
temperature is controlled between 32 and 32.5�F.
ONE DROP (less dehumidification) - The evaporator
temperature is controlled between 39 and 39.5�F.
TWO DROPS (less dehumidification) - The evaporator
temperature is controlled between 44.8 and 45.2�F.
ECON - The air conditioning compressor is sw1tched off, and
the system operates as a ventilator or heater only.
FACE VENTS SLIDER CONTROL
The outlet air temperature of the two SIDE fascia vents (and
centre fascia vents when opened - see NOTE below) can be
controlled by the sliding bar (but only as a reduction to
its temperature in relation to the temperature of the air at
the foot well vents). Full left decreases side vent air
temperature; full right increases side vent air temperature
up to the temperature of the air from the foot well.
NOTE NOTE NOTE:-
The vacuum controlled centre fascia vents ONLY open when
cool air is selected / demanded (e.g when aircon is working)
to provide more cool air at face level.
Any change in temperature selection etc can take up to 45
seconds to take effect (a built in delay to prevent
‘hunting’) - so be patient!
The twin blowers will not operate when ‘Heat’ is selected if
the engine coolant temperature passing through the climate
control unit is less than 85� F
There may be other little twists which I can’t now recall,
but if still in doubt, ask.–
The original message included these comments:
I’m sorry to have to ask this, but how do I operate the air
conditioner in my '89 xj40 3.6lt?
–
Bryan N, '91 Sovereign 4.0 L, RHD
Cambridgeshire, United Kingdom
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