PREVOST X3-45 COMMUTER User Manual

SECTION 22: HEATING AND AIR CONDITIONING
DOB 1300-1556 | X3-45 Commuter PA-1648 Maintenance Manual First release Oct 2020
23
4.6 MOISTURE INDICATOR
The moisture sensitive element consists of a
color-changing ring which is reversible from pink
to blue and vice versa as the moisture content in
the refrigerant changes.
•
PINK: high levels of
moisture detected.
• PURPLE (caution)
: low
levels of moisture detected.
•
BLUE: dry, optimal
operating conditions.
Since temperature changes affect the solubility,
color change will also vary with the refrigerant
temperature. The above table shows the color
change for R-134a at various moisture levels
and liquid line refrigerant temperatures.
MAINTENANCE
Check refrigerant moisture indicator
at the
intervals specified by the
Lubrication &
Servicing Schedule in Section 24A.
Replace filter-dryer unit according to moisture
indicator.
COLOR INDICATOR
TEMPERATURE
BLUE
(ppm)
LIGHT
VIOLET
(ppm)
PINK
(ppm)
75°F (24°C)
100°F (38°C)
125°F (52°C)
20
35
60
35
55
65
130
160
190
p.p.m.= parts per million (moisture content)
A moisture level of less than 15 p.p.m. for R-
134a indicated in the blue color range of the
above table is generally considered dry and
safe. A color indication of light blue to light violet
indicates the caution range of moisture level. For
positive protection, the drying of the system
should be continued until the color of the
element turns to deep blue.
The liquid refrigerant is readily visible through
the center opening of the moisture element
where the presence of bubbles or flash gas
indicates an insufficient system charge, low
head pressure, insufficient liquid sub cooling or
some form of restriction in the liquid line.
Moisture is one of the main causes of chemical
instability or contamination in air-conditioning
systems. If moisture is present, it can corrode
the valves, condenser and evaporator coils,
compressor and other components causing a
malfunction and eventual failure of the system.
Uncontrolled moisture in the system can result in
very expensive multiple component
replacements if not corrected at an early stage.
The moisture indicator permits an early
detection of moisture in the system and when
corrected by a desiccant charge, system
contamination is greatly minimized.
CLEAR
Normal, system OK
Temporary condition, normal when A/C
system is turned on. Wait a few minutes
for the system to stabilize.
BUBBLES, FOAMY
Low refrigerant level
Excessive pressure drop in filter dryer
Restricted filter dryer
MILKY, CLOUDED
Contaminated system
OIL STREAKS
Oil contamination
FIGURE 30: CONDITIONS THAT MAY BE OBSERVED IN
THE MOISTURE INDICATOR SIGHT GLASS
4.7 SHUTOFF VALVE WITH SERVICE
PORT
This shutoff valve (FIGURE 31) is located in the
condenser compartment. It is used to isolate one
section of the refrigerant circuit. The service port
is equipped with a Schrader valve.

PREVOST X3-45 COMMUTER Specifications

General

Engine	Volvo D13
Transmission	Allison B500
Fuel Type	Diesel
Length	45 ft (13.7 m)
Width	102 in (2.6 m)
Horsepower	500 hp
GVWR	54, 000 lbs
Height	141 in