climate control AUDI A8 2003 D3 / 2.G Technical Features Manual

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An optional feature for the Audi A8 ´03 is
4-zone climate control, enabling both driver
and all passengers to make individual
settings independently of the climate control
level selected for the other occupants.
Design and operation
The air conditioning system represents a
more advanced version of the concept
employed in the Audi A8 predecessor model
with 2-zone climate control and features fully
automatic regulation.
Heating/Air Conditioner
The following components are new features
as compared to the systems previously fitted
in the Audi A8:
– Humidity sender G355
– Evaporator outflow temperature sender
G263
– Two versions: 2-zone front climate control
with 12 control motors and 4-zone front
and rear climate control with 15 control
motors
– Rear climate control with electric rear
additional heater as additional equipment
("4-zone system") – rear left and rear right
footwell heater element Z42 and Z43
– Second control and display unit with
4-zone climate control, Climatronic control
unit J255, rear Climatronic control and
display unit E265– Climate control menu in MMI (Multimedia
Interface) for display of climate control set
values and basic settings
– Front and rear seat heating and seat
ventilation
– Heated windscreen Z2
– Energy management control unit J644
The interaction of these components in
coordination with the entire air conditioning
system forms a control loop and permits
comfortable front and rear climate control to
suit all requirements.
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A distinction is made between two air
conditioner unit versions
– 2-zone front and rear climate
control
– 4-zone front and rear climate
control
and three types of control and
display unit
– Air conditioner control panel with
no seat heating/ventilation
– Air conditioner control panel with
seat heating
– Air conditioner control panel with
seat heating and seat ventilation
(identified by part number index).
SSP282_099
Self-diagnosis
Fault diagnosis and measured value blocks
for air conditioner and seat heating system
can be read out by way of address words 08
"Air conditioner/heater electronics" and 28
"Rear climate control". The functions of and
exact procedure for self-diagnosis and
assisted fault-finding with VAS 5051 can be
found in the Heating/Air Conditioner
Workshop Manual for the relevant vehicle
model.
Operating principle
When the ignition is switched on, the
Climatronic control unit J255 starts up with
the same temperature, air distribution and
fresh-air blower speed settings etc. as were
applicable the last time the ignition was
switched off by way of the appropriate key or
using fingerprint recognition.
If fingerprint recognition has been
implemented, this has priority over key
recognition (refer also to SSP 287 – Audi A8 ´03
Electrical Components).
Personalised settings
The following settings can be made for each
climate control zone (front left, right and,
optionally, with 4-zone climate control rear left
and right):
– Left/right temperature
– Air flow
– Left/right air distribution
– Left/right seat heating
– Left/right seat ventilation
– Operating modes (AUTO for driver and front
passenger, temperature-adjustable centre
vents, automatically controlled
recirculated-air mode, ECON)
The heated windscreen can be activated by
way of the air conditioner defrost button or
the air conditioner control unit automatically
switches on the electric heated windscreen if
the appropriate conditions are satisfied
(windscreen defrost or automatic mode on
cold starting).
The Climatronic J255 and heated windscreen
J505 control units communicate by way of the
LIN bus. The Climatronic control unit transmits
the specified windscreen heating power to the
heated windscreen control unit on the LIN bus.
Heating/Air Conditioner
Key recognition takes place in the case of
remote control (radio or key transponder),
with the driver identification control unit
providing the Climatronic control unit J255
with the appropriate information by way of
the CAN bus.
The electrically heated windscreen is only
supplied with the amount of power which can
currently be drawn from the electrical system
without draining the battery. This is
monitored by the energy management
control unit J644.
As is the case with the Audi A4, the
windscreen is heated by applying voltage to a
metallic foil fitted in the glass (refer to
SSP 213).
As in the Audi A4, the air conditioner
compressor is regulated as a function of load
and controlled externally by way of the
compressor regulating valve (refer to
SSP 240). The Climatronic control unit J255 is
connected to the convenience CAN, via
which diagnosis is also performed.
A manual air conditioning system is not
available.

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Electric rear additional heater
An electric rear additional heater is fitted
under each front seat in the rear climate
control footwell air ducts.
Heating/Air Conditioner
A further advantage is that independent
temperature regulation (heating) can be
provided for the rear footwell with the 4-zone
system.
A supply of colder air to the rear climate zones
as opposed to the front can be achieved by
way of the centre chest vents.
The temperature can however only be reduced
but not increased via these vents through the
addition of cold air.
As in the predecessor model, two separately
controlled heat exchangers permit the setting
of different temperatures at front left/right.
All occupants can therefore be provided with
individual climate control. Operation
Following a cold start or at low ambient
temperatures, there is insufficient waste heat
in the coolant to warm the rear of the vehicle
by means of a conventional fluid-filled heater.
In addition, the drop in temperature in the rear
air duct is extremely high in the initial phase.
This problem has been solved by integrating
two electric rear additional heaters into the
rear footwell air duct.
These employ electrical energy from the
vehicle electrical system to heat the air
supplied to the passenger compartment.
In this way, the heating function is available
immediately following cold starting.
As was the case with the predecessor
model, in situ heat exchanger
replacement is possible. The procedure
involved is described in the current
Workshop Manual.
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The buttons for the seat heating and
ventilation options are integrated into the
front and rear control and display units
(refer to Page 74). Climate-controlled seats with heating and
ventilation function
The Audi A8 ´03 can be fitted with front and
rear climate-controlled seats as optional
equipment. These seats offer a combination
of seat heating and seat ventilation and can
be regulated individually for each occupant.
Heating/Air Conditioner
The corresponding feedback LED lights after
pushbutton activation of seat heating/seat
ventilation. The selected seat heating/seat
ventilation stage can be called up in the
display segment of the Climatronic control
unit J255 and in the MMI (Multimedia
Interface) climate control menu. Once seat
heating/seat ventilation has been activated, it
remains active even after switching off the air
conditioner by means of the ON/OFF button.The use of seat ventilation leads to lower
occupant skin temperatures. Automatic
additional seat heating operation controlled
as a function of temperature cancels the
cooling effect and the air flow is warmed.
The ventilation function promotes pleasant
conditions in the occupant's back and seat
area and eliminates sweating more quickly.
Under normal circumstances, the seat
ventilation function is deactivated
automatically after approx. 30 minutes.
SSP282_107 Seat heating
button
Seat ventilation
button

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Comfort seat
The seat heating and seat ventilation
functions are not incorporated into
automatic climate control mode.
Seat climate control is achieved by way of
integrated fans in the seat cushion and
backrest. Air ducts in the seat padding convey
the air warmed by the seat heating to the
occupant through the fine perforations in the
leather.
SSP282_108
Air ducts
in seat padding
Fan in seat cushion
Seat cushion
carbon heating mats Backrest carbon
heating mats
Side bolster
carbon heating matFan in backrest

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V50 N175 N176G238 G65 G107 G348 G347Z43 Z42
J126
V2Z45 G344 Z46
G345 3015
SS
15A5A
75
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25A
75
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25A
C20
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20A
N340G355
J528J533
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G89
G150 G151 G263
V221
V111 V110 V220
V102 V68 V109 V108 V199 V200 V107 V71 V113J255 V42 G5658S
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G143G113 G135
G318G317G139
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G138G351G136
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T16
Colour code
= Input signal
= Output signal
= Positive supply
= Earth
= Convenience CAN High
= Convenience CAN Low
= LIN busAdditional signals
Climate control LIN bus for
– Heated windscreen
control unit J505
– Driver seat ventilation
control unit J672
– Front passenger seat ventilation
control unit J673
1Terminal 30/blower
Terminal 30/front seat heating
Input/rear roller blind switch E1492
3
4
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