Range Rover P38
ELECTRONIC AIR SUSPENSION
3
DESCRIPTION AND OPERATION
DESCRIPTION OF COMPONENTS
Electrical Control Unit - ECU
The ECU is located underneath the front left hand
seat. The ECU maintains the requested vehicle ride
height by adjusting the volume in each air spring. It is
connected to the cable assembly by a 35 way
connector. To ensure safe operation the ECU has
extensive on board diagnostic and safety features.
The ECU must be replaced in case of failure.
Air compressor
NOTE: The air compressor and valve block
are contained in the under bonnet unit
mounted on the left hand inner wing.
The air compressor provides system pressure. A
thermal switch is incorporated which cuts out
compressor operation at 120
°
C. An air filter is fitted to
the compressor head. The filter is renewed every
40,000 kms (24,000 miles), or every 30,000 miles in
NAS markets.
Air dryer
The air dryer is connected into the air line between the
compressor and reservoir. It is mounted on the engine
air cleaner box. The dryer removes moisture from
pressurised air entering the system. All air exhausted
from the system passes through the dryer in the
opposite direction. The air dryer is regenerative in that
exhaust air absorbs moisture in the dryer and expels it
to atmosphere.
The air dryer is non-serviceable, designed to last the
life of the vehicle. However, if any water is found in
the system, the air dryer must be replaced.
CAUTION: If the air dryer is removed from
the vehicle the ports must be plugged to
prevent moisture ingress.
Valve block
The valve block controls the direction of air flow. Air
flow to and from the air springs is controlled by seven
solenoid operated valves, one for each spring plus an
inlet, exhaust and outlet. In response to signals from
the ECU, the valves allow high pressure air to flow in
or out of the air springs according to the need to
increase or decrease pressure. A diaphragm valve
operated by the solenoid outlet valve ensures that all
exhausted air passes through the air dryer.
Mounted on the valve block is a pressure switch which
senses air pressure and signals the ECU to operate
the compressor when required.The compressor will
operate when the pressure falls between 7.2 and 8.0
bar (104 and 116 lbf/in
2
). It will cut out at a rising
pressure of between 9.5 and 10.5 bar (138 and 152
lbf/in
2
).
The valve block contains the following serviceable
components: solenoid coils 1 to 6, drive pack and
pressure switch.
The valve block must only be dismantled after the
correct diagnosis procedure.
Reservoir
The 10 litre reservoir is mounted on the right hand
side of the chassis. One connection acts as air inlet
and outlet for the rest of the system. The reservoir
stores compressed air between set pressure levels.
The reservoir drain plug requires removing to check
for moisture in the system every 40,000 kms. (24,000
miles), or every 30,000 miles in NAS markets.
Height sensors
Four potentiometer type height sensors signal vehicle
height information to the ECU. The potentiometers are
mounted on the chassis and activated by links to the
front radius arms and rear trailing links. A height
sensor must be replaced in case of failure, and the
vehicle recalibrated using TestBook.