TM 5-3805-291-23-1
AIR CONDITIONING SYSTEM TESTS, INSPECTIONS, AND ADJUSTMENTS - CONTINUED
0018 00
N OT E - CON T I N U ED
Presence of frost on accumulator is a normalcondition. Thickness of frost will depend on
ambient temperature and humidity.
Frost can appear anywhere on a R-134a ACsystem. Appearance of frost does not always
indicate a failure. In order to diagnose a blockage in AC system properly, air tempera-
ture at evaporator must be checked and pressure readings must be taken.
All charging and leak testing mustbe done in a well ventilated area.
Avoid any physical contact with refrigerant.
Place a clean cloth over any valve orany connection that is opened.
Never weld any charged components.
Never solder any charged components.
Never steam clean any charged components.
Do not leave refrigerant drums exposed to direct sunlight.
Do not carry refrigerant drums intopassenger compartment of machine.
Dispose of any oil that is poly alkaline glycol (PAG) that has been opened but not used.
Moisture will contaminate unused oil and air conditioning system.
For a better understanding of each sysem, review the appropriate section in Theory of
t
Operation (WP 0003 00).
In order to check function of compressor, disconnect hose from inlet of inline dryer. Mea-
sure pressure of suction of compressor. Pressure should be a vacuum between 24 to 28
inHg (81 to 95 kPa). Do not operate compressor for more than 2 minutes when system
pressure is below vacuum.
Secure lines and wires in order toprevent damage to lines and wires.
Formation of black sludge depoits in system is caused by presence of moisture in R-134a
s
systems and by mixing charges of R-134a and R-12. Black sludge deposits can cause a
blockage in system.
Presence of white foam duringrecovery is normal. Foam is caused by mixing of oil and
refrigerant.
R-134a system charges must bewithin 1.000 to 2.000 oz (0.03 to 0.06 kg) of specified
charge for machine.
A drain line that is plugged or a drain line that is pinched may cause a backup of conden-
sate and leakage into cab.
Missing drain valves may cause a backupof condensate and leakage into cab.
Missing drain valves will alow dust to be sucked into evaporator coil and heater coil.
A cab pressure of 0.200 to 0.600 in. of H2O (0.05 to 0.15 kPa) and proper maintenance of AC filter will result in the fol-
lowing conditions:
Reduction of dust.
Reduction of noise.
More efficient HVAC performance.
0018 00-3
