SECTION 12: BRAKE AND AIR SYSTEM
DOB 2490-2789 | X3-45 Commuter PA1605 Maintenance Manual (Final Version – Rev.2 April 2016)
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Provides a rapid application of the spring
brake actuator when parking.
Modulates the spring brake actuator
application using the dual brake valve
should a primary failure occur in the service
brake system.
Prevents compounding of service and spring
forces.
Maintenance and repair information on the
spring brake valve is supplied in the applicable
booklet annexed to this section under reference
number SD-03-9043.
FIGURE 22: SR-7
12206
20. PRESSURE PROTECTION VALVE (PR-4)
Maintenance and repair information on the
pressure protection valve is supplied in the
applicable booklet annexed to this section under
reference number SD-03-2010.
The air system includes two pressure protection
valves (Figure 23). One valve is installed on the
manifold block, and insures at all times a
minimum pressure of 75 psi (517 kPa) in the
suspension air system in the event that a
pressure drop occurs in either the suspension
air system or accessory air system. This valve is
located in the front service compartment beside
the air filter.
FIGURE 23: PR-4
12174
The other valve is installed on the accessory air
tank, and insures a minimum pressure of 75 psi
(517 kPa) in the accessory air system in the
event that a pressure drop occurs in either the
suspension air system or braking air system
(refer to Figure 1 for accessory air tank location).
21. SHUTTLE-TYPE DOUBLE CHECK
VALVE (DC-4)
Maintenance and repair information on the
shuttle-type double check valve is supplied in
the applicable booklet annexed to this section
under reference number SD-03-2202.
The double check valve is located on the
pneumatic accessory panel in the front service
compartment. In the event of a pressure drop in
either the primary or secondary system, this unit
will protect the emergency /parking brake control
valve and the intact portion of the air system
from pressure loss.
FIGURE 24: DC-4
12134
22. EMERGENCY BI-FOLD ENTRANCE
DOOR OPENING VALVES
Two emergency door opening three-way valves
are installed on the coach. One is in the front
service compartment, readily accessible. The
other one is below the R.H. dashboard panel.
When used, the valve releases pressure in the
entrance door locking cylinders, thus allowing
the door to be manually opened.
FIGURE 25: THREE-WAY VALVE
12186
