Automatic Tag Axle Unloading; Driver Notification; Traction Control; Automatic Tag Unload Override Valve - PREVOST X3-45 Commuter 2020 Operating Manual

AUTOMATIC TAG AXLE UNLOADING

The tag axle unloads when the air pressure is
reduced in the air springs. The tag axle
automatically unloads in tight maneuvering areas
like in a parking lot to make it easier to turn a
short corner and to reduce excessive wear of the
tag axle tires.
The tag axle will unload automatically when all
the following conditions are met:
1. The ignition is ON;
2. The steering wheel's rotation exceeds one
turn;
3. The vehicle speed is below 20 mph.
In service, the tag axle will automatically reload if:
1. The vehicle speed exceeds 20 mph during 6
seconds;
or
2. The steering wheel's rotation becomes
less than 1/4 turn.
NOTE
To avoid flat spots on the tires, the tag axle
service brakes operate only when the tag axle is
loaded.

DRIVER NOTIFICATION

In normal operating condition of the vehicle, the
driver is not notified when the tag axle unloads
automatically due to the conditions mentioned in
the preceding paragraph.
If the tag axle is unloaded through the use of the
automatic tag unload override valve located in the
front service compartment, a pop- up message
will appear in the DID as the ignition is turned to
the ON position to warn the driver. Moreover, a
pop-up message will appear and a warning tone
will sound to warn the driver when the engine is
running and the vehicle speed exceeds 3 mph.
DOB 1300-1556
FIGURE 2: POP-UP MESSAGE
The following pictogram appears in the DID's
status bar to confirm that the automatic tag
unload override valve is switched to UNLOAD.
FIGURE 3: TAG AXLE UNLOAD SELECTED

TRACTION CONTROL

In service, the tag axle will unload when a
spinning wheel condition is detected. This action
is automatic and no action from the driver is
required. Unloading the tag axle transfers extra
weight for better traction to the drive wheels
providing improved control on slippery surfaces.

AUTOMATIC TAG UNLOAD OVERRIDE VALVE

The automatic tag unload override valve is
located in the front service compartment.
FIGURE 4: FRONT SERVICE COMPARTMENT
For maintenance purposes, use this valve to
override the automatic loading/unloading of the
tag axle.
The valve can be switched to UNLOAD or
NORMAL position. Switching to UNLOAD keeps
the tag axle unloaded at all time and cancels the
automatic loading or unloading function.
NOTE
Always return the override valve to NORMAL
before returning the vehicle to service.
PA-1639 Operator's Manual 2020 X3-45 Commuter
Other Features 5-37