SECTION 22: HEATING AND AIR CONDITIONING
DOB 2490-2789 | X3-45 Commuter PA1605 Maintenance Manual (Final Version – Rev.2 April 2016)
31
complete unit and replace with a new unit of the
same type according to this procedure:
1. Perform the pumping down procedure to
isolate refrigerant in the receiver tank.
2. Disconnect C24 to isolate the section of the
system located between the receiver tank
outlet shut-off valve and the passengers’
unit liquid solenoid valve.
3. Change the filter-dryer.
FIGURE 37: ISOLATED SECTION
4. Once the filter-dryer has been replaced, it is
necessary to evacuate the opened section
of the refrigerant circuit. Evacuate the
isolated section of the system using a
vacuum pump connected to the service port
of the receiver outlet shut-off valve.
5. Evacuate the section of the refrigerant
piping as needed and in accordance with
best practices, using a micron gauge to
monitor the depth of vacuum. Evacuate to a
system pressure less than 1000 microns.
6. Turn off the vacuum pump.
7. Backseat the outlet shut-off valve and then
disconnect the vacuum pump hose.
CAUTION
Do not use carbon tetrachloride or similar
solvents to clean parts. Do not use a steam
gun. Use mineral spirits or naphtha. All parts
should be thoroughly cleaned. Use a stiff
brush to wash dirt from grooves, holes, etc.
DANGER
Cleaning products are flammable and may
explode under certain conditions. Always
handle in a well-ventilated area.
7.7 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 every 50
000 miles or twice a year, whichever comes
first. 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
