Section 22: HEATING AND AIR CONDITIONING
PA1562
25
DANGER
Cleaning products are flammable and may
explode under certain conditions. Always
handle in a well ventilated area.
7.6.2 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 indicates a wet
refrigerant, light violet (caution) and blue
indicates a dry refrigerant.
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.
COLOR INDICATOR
TEMPERATURE
BLUE
(ppm)
LIGHT
VIOLET
(ppm)
PINK
(ppm)
75°F (24°C)
100°F (38°C)
125°F (52°C)
Below 5
Below 10
Below 15
5-15
10-30
15-45
Above 15
Above 30
Above 45
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 indicates a
shortage of refrigerant or restriction in 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.
7.7 LIQUID REFRIGERANT SOLENOID
VALVE
The flow of liquid refrigerant to the driver’s and
main evaporators is controlled by a normally-
closed solenoid valve. The driver’s liquid
solenoid valve is located on the ceiling of the
spare wheel and tire compartment and is
accessible through the reclining bumper.
FIGURE 30: DRIVER'S EVAPORATOR LIQUID SOLENOID
VALVE
22324
NOTE
An identical refrigerant solenoid valve is used
on the auxiliary A/C system and is located
near the auxiliary A/C unit.
7.7.1 Manual Bypass
This type of solenoid valve is equipped with a
manual operating stem. The 3/16" square stem
located on the bonnet is exposed when the seal
cap is removed. To manually open valve, turn
stem ½ turn counterclockwise. To manually
close valve, turn stem clockwise until tight
against seat. Manual stem must be in closed
position for automatic electric operation.
7.7.2 Coil Replacement
1. Disconnect connector from the coil
connector.
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