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Chapter 5
– System Controls
5-14
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Chapter Start - Table of Co
ntents- Index
• A balanced system is more efficient in moving heat energy
into or out of the air in the cab than an unbalanced one.
Balance means maintaining pressures and temperatures in-
side the system so that heat energy moves easily and effi-
ciently from one area to another.
• In most systems o
ne or more heat or pressure sensitiveswitches may be ins
talled. These usually protect the com-pressor if somethin
g goes wrong inside the system or the
refrigerant leaks out
.• The more advanced
system designs useair pressure or
vacuum for system and component control. Electronic con-
trols are also used. The advantages of advanced controls are
more even cab temperature and faster control response.
• The engine fan clutch and radiator shutter are controlled by
engine coolant temperature. In an AC system with an
underhood condenser, override controls are used to govern
fan clutch and radiator shutter operation.