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

3
Contents
Principles
Vehicle suspension.................................................................. 4
The suspension system .......................................................... 6
Vibration ................................................................................... 8
Characteristic values of springs .......................................... 12
Conventional running gear without self-levelling ............ 14
The self-study programme is not intended as a workshop manual.
The self-study programme will provide you with
information on design and functions.
New
NoteImportant:
Note
Page
For maintenance and repairs please refer to the current
technical literature.
Principles of air suspension
Self-levelling air suspension ............................................... 16
Characteristic values of air spring ...................................... 21
Vibration damping................................................................. 23
Shock absorbers (vibration dampers) ................................ 25
PDC shock absorbers ........................................................... 33
System overview ................................................................... 38
Air springs .............................................................................. 40
Air supply unit ........................................................................ 42
Diagram of pneumatic system ............................................. 43
Compressor ........................................................................... 44
Air dryer ................................................................................. 47
Discharge valve N111 ........................................................... 48
Valve for suspension struts N150 and N151....................... 51
Self-levelling suspension sender G84 ................................ 52
Self-levelling suspension control unit J197 ....................... 54
Self-levelling suspension warning lamps K134 ................ 55
Function diagram ................................................................... 56
Interfaces................................................................................ 57
The control concept .............................................................. 58
Other features of the control concept ................................ 60
Self-levelling suspension, A6

39
¥ Environmentally friendly, uses air
¥ Good operating safety due to great
stability.
¥ Electronic control system with
comprehensive self-diagnosis functions
¥ Maintenance-free Along with the principle advantages of self-
levelling (see Principles), the system realised
in the A6 has the following advantages:
¥ Virtually load-independent suspension
and vibration behaviour.
¥ Little space requirement due to compact
design, especially in the axle area.
¥ Self-levelling even available when engine
is off.
¥ Rapid raising and lowering times
¥ Low energy requirement
Air springs with PDC damperSelf-levelling suspension, A6 quattro
drive
Air supply unit242_041

47
The air dryer
The air must be dehumidiÞed in order to
prevent condensate and the associated
problems of corrosion and freezing. The
system used here is a so-called regenerative
air dryer system. A synthetically
manufactured silicate granulate is used as the
drying agent. This granulate can, depending
on the temperature, store up to 20% of its
own weight in water.
As the air dryer operates regeneratively, and
is only operated with oil-free, Þltered air, it is
not subject to replacement intervals and is
therefore maintenance-free.Because the air dryer is regenerated
only with waste air, the compressor
cannot be used to Þll any other
components. As this compressed air is
not fed back via the air dryer, no
regeneration can take place. For this
reason, the manufacturers do not Þt a
pressure connection for external
components.
Water/moisture in the system indicates
a fault in the air dryer or the system.
242_056 Granulate Þlling