TM 5-3805-280-24-1
Theory of Operation
REFRIGERANT THEORY OF OPERATION
A--B27 A/C High and Low
E--Condenser
J--Expansion Valve
N--M6 A/C and Heater
Pressure Switch
F--High Pressure Gas
K--Not Used
Blower Motor
B--Receiver/Dryer
G--Compressor
L--Low Pressure Liquid
C--High Pressure Liquid
H--Low Pressure Gas
M--B29 A/C Heater
9031
D--Engine Fan
I--Evaporator
Thermistor
05
2
condenser fan (D). Cooling the refrigerant causes it to
The compressor (G) draws low pressure gas (H) from
condense and it leaves the condenser as a high
the evaporator (I) and compresses it into high pressure
pressure liquid (C). The high pressure liquid flows into
gas (F). This causes the temperature of the refrigerant
the receiver-dryer (B) where moisture and
to rise higher than that of the outside air.
contaminants (acid, solids, etc.) are removed. The
receiver-dryer also acts as a reservoir for refrigerant.
High pressure gas leaves the compressor and is
sensed by the high pressure part of the B27 A/C high
The refrigerant flows from the receiver-dryer to the
and low pressure switch (A). The switch monitors
expansion valve (J) and is sensed by the low pressure
refrigerant pressure. If the pressure becomes too high,
part of the B27 A/C high and lower pressure switch
the switch will open and stop the compressor,
(A). The switch monitors refrigerant pressure. If the
interrupting the cycle.
pressure becomes too low from refrigerant loss, the
switch will open and stop the compressor, interrupting
As the high pressure gas flows through the condenser
the cycle.
(E), heat is removed and transferred to the outside air
being drawn through the condenser core by the
Continued on next page
TX,9031,UU3137 1913AUG961/2
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