Pressure Regulating Valves; Maintenance; Pressure Setting Procedure; Air Compressor - PREVOST H3-41 Maintenance Manual

securely located in position and free from any
binding condition, which would hinder air flow.

11. PRESSURE REGULATING VALVES

There is one pressure regulator (Figure 10) for
small A/C compressor
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)
30 ± 3
Belt
(Single belt)
Tensioner
45 ± 3
(Dual belts)
Retarder 80+0/-5
11.1

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 10). Examine
the diaphragm; if cracked, worn or damaged,
replace with a new one. If the valve is excessive-
ly 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.
and accessories
Air Pressure
(kPa)
± 20
207
± 20
310
35
552 +0/-
PA1621 Maintenance Manual All Series | Revised June 2020
SECTION 12: BRAKE AND AIR SYSTEM
FIGURE 10: AIR PRESSURE REGULATING VALVE

11.1.1 Pressure Setting Procedure

Remove the dust cap from the pressure check
port (Figure 11). Attach a pressure gauge at this
port and check the pressure reading. If the
pressure reading is incorrect, adjust as follows:
12. Loosen the locking nut; turn the adjustment
screw counterclockwise to decrease pressure
by approximately 10 psi (70 kPa) below the
required pressure.
13. Turn the adjustment screw clockwise to
increase the pressure
required pressure setting is reached. Tighten
the locking nut.
14. Remove pressure gauge and replace dust
cap on the pressure check port.
FIGURE 11: AIR PRESSURE REGULATOR (H-SERIES)

12. AIR COMPRESSOR

The Wabco System Saver 636 Twin Cylinder air
compressor is located on the right side of the
engine, at the flywheel end (Figure 12). Its
slowly until the
15