SECTION 12: BRAKE AND AIR SYSTEM
14
PA1621 Maintenance Manual All Series | January 2017
chafing or cutting may occur. Replace with new
material as required. In general, lines should be
securely located in position and free from any
binding condition, which would hinder air flow.
10. PRESSURE REGULATING VALVES
There is one pressure regulator (Figure 8) for
small A/C compressor and accessories
alternator drive belt tensioner, and an optional
one installed on vehicles equipped with the
world transmission output retarder.
The belt tensioner pressure regulating valve is
located in the engine compartment above the
engine air filter and is used to limit the air
pressure in belt tensioners to 30 ± 3 psi (207 ±
20 kPa) for vehicles equipped with a single belt
and 45± 3 psi (310± 20 kPa) for vehicles with
dual belts arrangement.
The optional regulator is located in the engine
compartment, on the engine cradle R.H. side
(accessible through the engine R.H. side door).
It is used for transmission retarder and should
be adjusted to 80 +0/-5 psi (552
+0/-35 kPa).
Air Pressure
(psi)
Air Pressure
(kPa)
Belt
Tensioner
30 ± 3
(Single belt)
207
± 20
45 ± 3
(Dual belts)
310
± 20
Retarder 80+0/-5
552 +0/-
35
10.1 MAINTENANCE
Every 100,000 miles (160 000 km) or once every
two years, whichever comes first, disassemble
the pressure regulating valve and wash all metal
parts in a cleaning solvent (Figure 8). Examine
the diaphragm; if cracked, worn or damaged,
replace with a new one. If the valve is
excessively grooved or pitted, it should be
replaced. Replace any other part that appears
worn or damaged. After reassembly, adjust to
the specified pressure setting and check for air
leakage.
FIGURE 8: AIR PRESSURE REGULATING VALVE
10.1.1 Pressure Setting Procedure
Remove the dust cap from the pressure check
port (Figure 9). Attach a pressure gauge at this
port and check the pressure reading. If the
pressure reading is incorrect, adjust as follows:
8. Loosen the locking nut; turn the adjustment
screw counterclockwise to decrease
pressure by approximately 10 psi (70 kPa)
below the required pressure.
9. Turn the adjustment screw clockwise to
increase the pressure slowly until the
required pressure setting is reached. Tighten
the locking nut.
10. Remove pressure gauge and replace dust
cap on the pressure check port.
FIGURE 9: AIR PRESSURE REGULATOR (H-SERIES)
11. AIR COMPRESSOR
The Wabco System Saver 636 Twin Cylinder air
compressor is located on the right side of the
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