cooling AUDI A6 ALLROAD 1999 C5 / 2.G Pneumatic Suspension System

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Motorway mode
If the vehicle travels for longer than
30 seconds at over 120 km/h (vehicle is
already at normal level), it will automatically
be lowered to low level.
This reduces air resistance (saves fuel) and
lowers the vehicle’s centre of gravity
(improved driving dynamics).
PL (=HL1) is only cancelled when a
driving speed of 80 km/h is exceeded
(see automatic lowering) or when
switching to a lower level manually.
If the vehicle is already in HL2 it is not
lowered to parking level.
Manual mode
The motorway mode and parking level
control functions are deactivated in
manual mode (see Automatic
switching page 9).
The vehicle rises automatically to normal level
at the following speeds and time thresholds:
Vehicle speed Time
<70 km/h >120 seconds
<35 km/h >30 seconds
<5 km/h immediately

Parking level control
The parking level ensures that the vehicle is
maintained at a suitable level after parking for
a long period of time (normal volumetric
reduction due to cooling or diffusion).
It also facilitates entering and loading the
vehicle and optimises the appearance of the
stationary vehicle.
The parking level corresponds to high level 1
(HL1).
The vehicle is set to parking level
–when the system is in run-on mode and the
vehicle is locked from the outside.
–when sufficient pressure is present in pres-
sure accumulator.
–when the system is not switched to manual
mode.

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Level change process:
Raising - rear axle first, then front axle
Lowering - front axle first, then rear axle
Modes
Height mode/driving mode
Reaction times upon level deviation
Control characteristics during level change
Level change is basically performed axle by
axle, whereby level differences between the
left and right sides are compensated (e.g. if
loaded on one side).Driving speed Reaction time
<5 km/h
Height modeapprox. 5 seconds
approx. 1 second at
extremely low level
>10 km/h
Driving modeapprox. 50 seconds or
15 minutes
depending on the level
deviation
Run-on mode/run-up mode
The run-on mode enables the compensation
of level deviations after the vehicle has been
parked (e.g. caused by passengers leaving the
vehicle or unloading the vehicle) and before
driving off (e.g. caused by intense cooling,
leakage or loading).
In this mode, delay times before commencing
a journey are kept to a minimum.After “Ignition OFF”, the control unit is in the
so-called run-on mode. The control unit
remains active for a maximum of 15 minutes
(via terminal 30) until it goes into sleep mode.
Due to the limited energy available when the
engine is switched off, control limits are
extended and controls are limited in both
number and duration.