The valves are controlled by the SAMS electronic control unit (ECU). The ECU provides the
brains
for
the Smart Air Management System. The ECU contains the system specific program to control the vehicle
ride height, as defined by Blue Bird’s engineering specifications for system operation. The ECU receives
signals from various system components, i.e. height sensors, pressure transducers, inclination sensors, and
the user control panel (mode of operation) to provide system control for obtaining the desired vehicle ride
height.
With no power applied to the valve coils, they are in a de-energized condition. This allows an internal
spring to expand and pushes a plunger against the associated manifold port, thereby sealing off the
internal air passage. The stem of the plunger contains two-neoprene rings to serve as a guide to provide
true and even travel within the body of the valve assembly. The face of the plunger also contains a seal
that when forced against the seat of the manifold, provides a positive seal to prevent air flow through the
manifold when the valves are de-energized. This mechanical action enables the SAMS system to seal the
air within the system and maintain the desired ride height.
Note:
The ports of the manifold contain a mesh screen to help prevent air contaminates from entering the
manifold. However, it is possible for the screen to become damaged and allow contaminates to enter the
manifold. Should this occur, it is possible for debris to collect on the plunger face seal or cause the
plunger to stick open, thereby affecting
system operation and performance.
Should an inflation valve plunger become contaminated or the plunger stick “open”, it is possible for
air to leak past the plunger and continuously fill the associated air bag. This would cause a corner of the
vehicle to continuously creep “upwards” while the vehicle is in operation, and result in the SAMS system
constantly making corrections to lower the affected corner of the vehicle.
Should an exhaust valve plunger become contaminated or the plunger stick “open”, it is possible for air
to leak past the plunger and continuously exhaust the associated air bag. This would cause a corner of
the vehicle to continuously creep “downwards” and result in the SAMS system constantly making
corrections to raise the affected corner of the vehicle. It should be noted that this condition would be
most noticeable after the vehicle has not been in operation for a period of time because the respective
corner of the vehicle would lean.
Note: An external leak, such as a loose air fitting, defective air bag, or tube leak could also cause the
vehicle to lean when not in operation for a period of time. External leaks can be detected by squirting
a suitable inspection solution, i.e. soap, water, & glycerin mix onto the external system components. If
an air leak is present, air bubbles will be created in the applied solution.
If either of these conditions is noticed, the vehicle should be inspected and the cause of the problem
corrected. These conditions could eventually cause premature compressor failure due to overheating from
excessive cycling. The compressor would attempt to maintain system pressure that would continuously
fluctuate due to the ECU trying to compensate for the system problem.
