Komatsu 930E-2, Shop Manual

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(HFC) refrigerant, commonly identified as HFC-134a, is being used in most current mobile air conditioning sys-
tems. Additionally, the practice of releasing either refrigerant to the atmosphere during the charging/recharging pro-
cedure is now prohibited.
These new restrictions require the use of new equipment and new procedures which are significantly different from
those traditionally used in air conditioning service techniques. The use of new equipment and techniques allows for
complete recovery of refrigerants, which will not only help to protect the environment, but through the “re-cycling”
of the refrigerant will preserve the physical supply, and help to reduce the cost of the refrigerant.
OPERATOR CAB AIR CONDITIONING
Mining and construction vehicles have unique charac-
teristics of vibration, shock-loading, operator changes,
and climate conditions that present different design
and installation problems for Air Conditioning systems.
Off-highway equipment, in general, is unique enough
that normal automotive or highway truck engineering
is not sufficient to provide the reliability to endure the
various work cycles encountered.
The cab tightness, insulation, and isolation from heat
sources is very important to the efficiency of the sys-
tem. It is advisable to close all vents, even the intakes
of pressurization systems, when there are high humid-
ity conditions.
The general cleanliness of the system and components
is important. Dust or dirt collected in the condenser,
evaporator, or air filters decreases the system’s cooling
capacity.
The compressor, condenser, evaporator units, hoses
and fittings must be installed clean and tight and be
capable of withstanding the strain and abuse they are
subjected to on off-highway vehicles.
Equipment downtime costs are high enough to encour-
age service areas to perform preventative maintenance
at regular intervals on vehicle air-conditioning systems.
(Cleaning, checking belt tightness, and operation of
electrical components).
PRINCIPLES OF REFRIGERATION
A brief review of the principles of air conditioning is
necessary to relate the function of the components, the
technique of trouble shooting and the corrective action
necessary to put the A/C unit into top operating effi-
ciency.
Too frequently, the operator and the serviceman over-
look the primary fact that no A/C system will function
properly unless it is operated within a completely con-
trolled cab environment. The circulation of air must be
a directed flow. The cab must be sealed against seep-
age of ambient air. The cab interior must be maintained
for cleanliness, dust, and dirt which, if picked up in the
air system, will clog the intake side of the evaporator
coil.
AIR CONDITIONING
Air conditioning is a form of environmental control. As
applied to the cab, it refers to the control of tempera-
ture, humidity, cleanliness, and circulation of air. In the
broad sense, a heating unit is as much an air condi-
tioner as is a cooling unit. The term “Air Conditioner”
is commonly used to identify an air cooling unit. To be
consistent with common usage, the term “Air Condi-
tioner” will refer to the cooling unit utilizing the princi-
ples of refrigeration; sometimes referred to as the
evaporator unit.
M9-2 Air Conditioning System M09010 6/97
for HFC 134a Refrigerant