Spicer TPCS (Tire Pressure Control System) Service Manual - Manual (Page 10)

10
System Operation
A vehicle equipped with the Tire Pressure Control
System will seem to operate the same as a vehicle
without the Tire Pressure Control System, however,
there are some differences:
• During normal operation, the Electronic
Control Unit will check tire pressures every 15
minutes to make sure that pressures are
maintained at selected settings.
• Immediately after a pressure change, the
pressure is rechecked after approximately
30 seconds.
• During the run flat mode, tire pressures are
checked at an increased rate.
During all of the above checks, solenoid clicking and air
exhausting from the Pressure Control Unit may be
heard.
The following is a description of how the Tire Pressure
Control System functions. Figure 2 shows a simplified
schematic of how the components of the system relate
to one another.
Pressure Regulation
The Tire Pressure Control System regulates tire pres-
sures through a series of electro-pneumatic controls
that supply air to each wheel end through wheel valves.
The driver operates a dash-mounted, graphic-control
panel (the Operator Control Panel) which commands
the system to adjust tire pressure.
Pressure Mode
The driver selects a desired tire pressure mode by
pressing buttons on the Operator Control Panel. The
system responds by adjusting tire pressures to match
the road surface and load. Indicators on the Operator
Control Panel inform the driver of functions currently
being performed.
Operator Control Panel
The Operator Control Panel also contains a built-in
indicator to warn drivers when they are travelling too
fast for selected tire pressures. If the vehicle’s speed is
not reduced, the Tire Pressure Control System will
automatically select the appropriate pressure. Addition-
ally, a warning icon will inform the driver to stop and
check the tires if the system senses conditions that may
indicate tire damage.
Air Seal Life
When the Tire Pressure Control System is idle, not
inflating, deflating or checking pressure, all tire air
pressures are isolated from the Tire Pressure Control
System. Tire pressure isolation extends seal life
because the seals are not under continuous pressure.
Isolation also provides fail-safe operation of the vehicle
if the Tire Pressure Control System is disabled.
Operation