maintenance BMW X5 1999 E53 Workshop Manual

Air Supply System (LVA)
The air supply system is identified as the LVA in the diagnosis program and in the repair
manual. It is mounted in the spare tire well compartment. The components are housed in
a sound deadening carrier, through rubber bushings, to prevent operating noises from
being transmitted through the vehicle’s interior.
With the exception of the compressor relay, individual replacement parts for the air supply
system are not available. If diagnosis determines a defect in any of the other air system
components, complete replacement is necessary.
The air supply system consists of the following components:
• Compressor assembly with;
- Piston compressor
- Electric motor
- Air dryer (desiccator)
- Pressure relief solenoid valve
- Pressure maintenance valve
- Check valves
• Compressor Relay (Replaceable)
• Solenoid Valve Block (2 - two way valves)
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Air Supply System (LVA) Operation
The single stage piston compressor produces a maximum pressure of 13.5 Bar. The com-
pressor is maintenance free - provided it is used in a dust free environment. This includes
the compressor’s intake air filter.
The compressor is driven by a DC motor that is controlled by the compressor relay through
the control module.
When the compressor is activated, the pressure builds up to a working pressure of 11.4
Bar (+0.8/-1.5 Bar). This is controlled through the pressure maintenance valve. The air
under pressure is fed through the dryer and check valve to the solenoid valve block for the
air springs.
There is one solenoid valve in the valve block for each air strut. This allows the system to
compensate for uneven loads in the vehicle and maintain the vehicles ride height at all
times.
Pressure is drained through the left or right solenoid valve (energized open) the pressure
relief solenoid valve, restricter, check valve and dryer back to the inlet side of the compres-
sor pump.
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Power Distribution
The maintenance free 90 AH battery
in the X5 is mounted in the rear below
the spare tire and EHC compressor
unit. The battery box is formed of
molded plastic and the positioning of
the battery aids in weight distribution.
As with all BMW vehicles, the battery
is equipped with the BST on the pos-
itive battery cable.
Power distribution for the vehicle and
systems is through two fuse carriers
mounted in the right storage com-
partment in the rear and above the
glove box in the front.
The battery jump/charge point is
located in the engine compartment on
the left side of the fire wall.
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