PREVOST X3-45 2016, Руководство по обслуживанию, Страница: 437 / 459

Section 22: HEATING AND AIR CONDITIONING
PA1593
39

Valve Troubleshooting
PROBLEM PROCEDURE
Valve fails
to close
1. Check electrical supply with a
voltmeter. It should agree with
nameplate rating.
2. Check pressure at pilot
solenoid valve inlet. It must be
at least equal to the minimum
pressure stamped on the
nameplate. It should not go
below minimum while valve is
operating.
1. Check that the closure
member assembly, and that
main actuator and cylinder
springs are free to travel.
2. Check that there is no
restriction to the air escaping
from the actuator casing.
3. Make sure that pilot solenoid
valve operates properly.
8.6 CENTRAL HOT WATER PNEUMATIC
VALVE ASSEMBLY

Description
The flow of hot water to the vehicle's central
heater core is controlled by a 3-way pneumatic
water valve assembly. The valve, located in the
evaporator compartment, is designed so that the
pilot solenoid valve, which is part of the
assembly, opens and closes a port which directs
air pressure to the actuator casing, thereby
allowing the hot water to enter the main heater
core or bypassing it.
When the vehicle is operating with no current to
the pilot solenoid valve, no air pressure is
admitted to the actuator casing, the cylinder
spring pushes up against the cylinder, thereby
allowing the hot water to enter the main heater
core.
The central heater water valve requires a
minimum amount of maintenance. The valve
should be free of dirt sediment that might
interfere with its operation. No other
maintenance is needed unless a malfunction
occurs.

Pneumatic Water Valve Disassembly
1. Shut off air supply pressure and electrical
current to the pilot solenoid valve.
Disconnect wires.
2. The water valve need not be removed from
the line. Unscrew nipple, the actuator
casing, tube, spindle and closure member
can be removed (Fig. 44).
3. Remove the snap ring using a pair of pliers.
FIGURE 43: CENTRAL HOT WATER PNEUMATIC VALVE
ASSEMBLY
22329
4. You can now access all seals for
replacement
Pneumatic water valve replacement seal
kits:
* Water Side: 871389
* Actuator Side: 871388

Pneumatic Water Valve Reassembly
1. Assemble the actuator casing, tube, nipple,
spindle and closure member.
2. Tighten the nipple in place in the body cavity
as per figure 44. Fasten pilot solenoid vale
to the pneumatic water valve. Reconnect air
supply pressure and electrical current to the
pilot solenoid valve.
3. Check for proper operation.

Pilot Solenoid Valve
1. No maintenance is needed unless a
malfunction occurs.