Bendix Commercial Vehicle Systems eTrac Automated Air Pressure Transfer System - Manual (Page 2)

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2. DESCRIPTION
The system features two states (with or without the Mud/
Snow switch engaged) and three modes (Normal/inactive;
System Active, and Pressure-Limiting Modes):
Mud/Snow Dash Switch Not Engaged
When the Mud/Snow dash switch is not engaged, the three
modes of operation are:
●
Normal (“automatic”) Mode is ready whenever the
vehicle is moving at less than 25 MPH. In this mode
the system behaves just like a typical air suspension
leveling system that adjusts for different loads by a
mechanical leveling (height control) valve that adjusts
all four rear suspension air bags as needed.
See Figure 3.
● The
Active Mode occurs when the vehicle encounters
road conditions where automatic traction control (ATC)
is activated. In addition to the actions of the Bendix ®
Smart ATC system, the Bendix ® eTrac ™ system
automatically vents (“dumps”) air pressure from the
tag axle air bags. See Figure 4.
With the drop in air pressure in the tag axle, the leveling
valve normal function adds air pressure to the drive axle
suspension air bags. When the air pressure reaches
a pre-determined maximum, the system enters the
Pressure Limiting Mode.
● The Pressure-Limiting Mode prevents system air
pressure delivery to the drive axle suspension air bags
above a pre-determined maximum pressure. The
system will then — using the backfeed valve — permit
the leveling valve to add air back into the tag axle
suspension air bags as needed. See Figure 5.
Automatic activations are terminated five (5) seconds after
the end of an ATC event, and are not able to be initiated at
vehicle speeds above 25 MPH.
Mud/Snow Dash Switch Engaged
This mode is sometimes called “semi-automatic” since
the driver engages the Bendix eTrac system, however the
system automatically terminates five (5) seconds after the
vehicle reaches ten (10) MPH.
By activating the Mud/Snow dash switch, the driver can be
proactive in anticipating slippery conditions. For example,
a driver — moving at five (5) MPH approaching a section of
road that is coated with mud — may anticipate this problem
zone and press the Mud/Snow switch. The Bendix eTrac
system will immediately enter the Active Mode described
above. When the drive axle reaches the pre-determined
maximum pressure, the Pressure-Limiting Mode (described
above) will be entered.
[It is useful to note that other systems where the driver is
responsible for remembering to disengage the air transfer
(typically by using a dash button) can lead to significant
damage to the driveline if left active.]
GENERAL SAFETY GUIDELINES
WARNING! PLEASE READ AND
FOLLOW THESE INSTRUCTIONS
TO AVOID PERSONAL INJURY OR DEATH:
When working on or around a vehicle, the following
guidelines should be observed AT ALL TIMES:
▲ Park the vehicle on a level surface, apply the parking
brakes and always block the wheels. Always wear
personal protection equipment.
▲ Stop the engine and remove the ignition key when
working under or around the vehicle. When working
in the engine compartment, the engine should be shut
off and the ignition key should be removed. Where
circumstances require that the engine be in operation,
EXTREME CAUTION should be used to prevent personal
injury resulting from contact with moving, rotating,
leaking, heated or electrically-charged components.
▲ Do not attempt to install, remove, disassemble or
assemble a component until you have read, and
thoroughly understand, the recommended procedures.
Use only the proper tools and observe all precautions
pertaining to use of those tools.
▲ If the work is being performed on the vehicle’s air brake
system, or any auxiliary pressurized air systems, make
certain to drain the air pressure from all reservoirs
before beginning ANY work on the vehicle. If the vehicle
is equipped with a Bendix ® AD-IS ® air dryer system, a
Bendix ® DRM ™ dryer reservoir module, or a Bendix ®
AD-9si ™ air dryer, be sure to drain the purge reservoir.
▲ Following the vehicle manufacturer’s recommended
procedures, deactivate the electrical system in a manner
that safely removes all electrical power from the vehicle.
▲ Never exceed manufacturer’s recommended pressures.
▲ Never connect or disconnect a hose or line containing
pressure; it may whip. Never remove a component or
plug unless you are certain all system pressure has
been depleted.
▲ Use only genuine Bendix ® brand replacement parts,
components and kits. Replacement hardware, tubing,
hose, fi ttings, etc. must be of equivalent size, type
and strength as original equipment and be designed
specifi cally for such applications and systems.
▲ Components with stripped threads or damaged parts
should be replaced rather than repaired. Do not
attempt repairs requiring machining or welding unless
specifi cally stated and approved by the vehicle and
component manufacturer.
▲ Prior to returning the vehicle to service, make certain all
components and systems are restored to their proper
operating condition.
▲ For vehicles with Automatic Traction Control (ATC),
the ATC function must be disabled (ATC indicator
lamp should be ON) prior to performing any vehicle
maintenance where one or more wheels on a drive axle
are lifted off the ground and moving.
▲ The power MUST be temporarily disconnected
from the radar sensor whenever any tests USING A
DYNAMOMETER are conducted on a Bendix ® Wingman ®
Advanced ™ -equipped vehicle.
▲ You should consult the vehicle manufacturer's
operating and service manuals, and any related
literature, in conjunction with the Guidelines above.