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

4
Description of the system
The vehicle level is determined separately at
each axle side by means of 4 level sensors.
Each air suspension strut is allocated a so-
called air spring valve (transverse check valve)
so that each axle can be controlled
individually.
Front right air
suspension strutRear left suspension strut with load-
dependant damping.
Rear left vehicle
level sender
Control unit
Pressure accumulator
Operating unit
Rear left suspension strut
with load-dependant
damping.
Air supply unit with: Compressor
Discharge valve
Transverse check valves
Temperature sender
Pressure sender
Rear right vehicle
level sender
Electrical/pneumatic
lines
Front left air
suspension strut
Front left vehicle
level sender
Front right vehicle
level sender

The 4-level air suspension system is a fully-
supporting level control system with
conventional shock absorbers at the front
axle and load dependent shock absorbers
(PDC dampers) on the rear axle.
243_021

14
The air springs
The front air spring is a new design.
As on the rear axle, the air springs are combined
coaxially with the dampers as a suspension strut.
The rear air springs are identical in design and
function to those of the Audi A6 with self-levelling.
Design
While in the case of the rear suspension strut, the
connection/seal from the air spring (piston) to the
damper is made via a double-seal bayonet
connection, on the front suspension strut it takes the
form of a single-seal N17 connector.
The differences in design require a different
assembly.
Front suspension strut
The assembly of the front air spring with the damper
is carried out without lubrication. The N17 connector
and the O ring must be absolutely dry and free from
grease.
Before assembly of the air spring, the O-ring
is placed onto the second shoulder of the damper,
ensuring an even perimeter. The air spring (piston) is
positioned onto the damper and pushed together
with adequate force. The O-ring is forced onto
shoulder 3 by the movement of the piston, where it
supports and seals the air spring.
System components
243_004
Installation
O-ring
O-ring
Air connection

15
Rear suspension strut
The bayonet connection must be absolutely
clean and is greased with a special lubricant
before installation (see Workshop Manual).
For installation, the air spring is pushed on
and then turned.
Operating pressure of the air springs
front rear
Minimum
operating
pressure6.0 bar 6.1 bar
Nominal
operating
pressure6.4 bar 8.5 bar
Maximum
operating
pressure9.0 bar 10.9 bar
Always check for leaks on the O-ring
seals at the raised areas. The sealing
surfaces must be clean, free from
corrosion and pitting (aluminium parts)
and greased as required (see Workshop
Manual).
Design and function of the rear air
springs, see SSP 242, from page 40
onwards.
Full description of the PDC damper, see
SSP 242, from page 33 onwards.

243_005
O-ring
Locking cap

33
Key to function diagram
E281 Self-levelling suspension operating
unit
F216 Contact switch for switchable rear fog
light
G76 Self levelling suspension sender, RL
G77 Self levelling suspension sender, RR
G78 Self levelling sender, FL
G289 Self levelling suspension sender, FR
G290 Compressor temperature, self-
levelling suspension sender
G291 Self-levelling suspension pressure
sender
J197 Self-levelling suspension control unit
J403 Relay for self-levelling suspension
compressor
J429 Control unit for central locking
J431 Control unit for headlamp range
control
N111 Discharge valve for self-levelling
suspension
N148 Valve for FL suspension strut
N149 Valve for FR suspension strut
N150 Valve for RL suspension strut
N151 Valve for RR suspension strut
N311 Valve for self-levelling suspension
pressure accumulator
K134 Self-levelling suspension warning
lamp
V48 Left headlamp range control motor
V49 Right headlamp range control motor
V66 Self-levelling suspension compressor
motor= Input signal
= Output signal
= Positive
= Earth
= Bi-directional
= CAN bus/signal wire
Auxiliary signals:
CAN low
CAN high
Door contact signal
Diagnostic connector for K wire
Vehicle locked signal
Trailer operation signal (F126)
Terminal 50 signal
Driving speed signal
Terminal 56
Diagnostic connector for K wire
to the instrument cluster
Driving speed signal from ABS control unit,
speed sensor output, rear left
1
2
3
4
5
6
7
8
I
II
III
IV
Terminal 58s
Terminal 58d
ESP button
ESP button
A
B
C
DHeadlamp range control signal
9
Power supply J431
10