Hudson 1955 Rambler, Техническое и сервисное руководство

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16 TECHNICAL SERVICE MANUAL
The low pressure liquid admitted to the evaporator
by the expansion valve vaporizes due to the heat
which it absorbs from the air passing over the
evaporator surface. This is the principle of
"Latent Heat of Vaporization" that is utilized to
vaporize the liquid Freon in the evaporator core.
The B.T.U.s or a certain quantity of the heat in
the air is used to vaporize the liquid. As it boils
it to a vapor, the heat is retained in the vapor—
and is carried along to the compressor. In turn,
to the condenser where the heat is given up to the
atmosphere as the vapor is condensed. This
absorption of heat from the air results in a
reduction in the air temperature. It is where the
refrigerant is changed from a liquid to a vapor.
Blower Unit
The blower fan is a high capacity squirrel cage
type.
The air is drawn into the evaporator unit
housing from the passenger compartment through the
heat distribution duct and the return air duct by
the blowers. The blower is located directly over
the evaporator core and beneath the heater core.
The fresh ram air admitted to the evaporator from
the cowl vent is combined with this air passing
over the evaporator core.
The air conditioning cycle is completed at this
point. The evaporated refrigerant, in a vapor
state, carrying the heat removed from the passen-
ger compartment continues back to the compressor
through the low pressure suction line. The cycle
is again started and repeated.
BY-PASS CYCLE
The continuous cycle of air conditioning has been
outlined. If this operation were carried on
continuously, the temperature would be drawn down
to a very uncomfortable level. A control must be
introduced into the system to prevent this
condition. Also, if the cycle were allowed to run
continuously, the evaporator core would frost and
eventually block the flow of air over the evapora-
tor and thus cooling would be stopped.
One method to control the amount of air
conditioning desired is by the operator's use of
the air conditioning switch. To pull the tempera-
ture down initially, "High" blower is used. When
the temperature is lowered to a comfortable level,
"Low" blower is used to maintain a comfortable
level in the car.
Another method of control is the automatic
by-pass cycle built into the system. The compo-
nents of this part of the system are the solenoid
by-pass valve, temperature control thermostat, and
check valve and manifold line (Fig. 20).
The solenoid by-pass valve is wired in series
to the temperature control thermostat and air
conditioning switch. When the switch is turned on,
the blowers and the solenoid by-pass valve are
energized, the valve is closed, and normal air
conditioning cycle takes place.
When the temperature of the evaporator reaches
the frost point, the solenoid by-pass valve is
de-energized by the temperture control thermostat
and the by-pass line will open. With the by-pass
line open, the pressure on the inlet side of the
check valve is less than the pressure on the outlet
side. The pressure present in the receiver then
closes the check valve. The refrigerant vapor is
then by-passed back to the compressor. The
pressures of the high and low side are partially
equalized. A modified amount of refrigerant is
directed to the evaporator. Therefore, air cooling
is reduced at this time.
Check Valve
The check valve prevents liquid refrigerant from
entering the by-pass and low pressure lines when
the solenoid valve is open. In turn, this will
prevent liquid refrigerant from entering the
compressor during a by-pass cycle I Fig. 22).
The valve has a spring loaded seat and operates
by differences in pressure at each end of the
valve. During refrigeration, the check valve is
open as the pressure in the condenser is slightly
higher than that in the receiver. During the time
the system is not refrigerating, the pressure in
the receiver becomes higher and the check valve
closes.
Temperature Control Thermostat
The solenoid by-pass valve is controlled during
the refrigeration cycle by the temperature control
thermostat located on the top of the evaporator
housing.
The capillary sensing tube is located in the
coldest section of the evaporator core. The
temperature control thermostat is wired in series
from the air conditioning switch to the solenoid
by-pass valve. This unit is pre-set at the factory
and no attempt to adjust it should be made by
service personnel.
Temperature Control Thermostat
Operation
The temperature control thermostat controls the
cycling operation of the system. It also prevents
the evaporator core from becoming frosted. By
cycling the refrigeration, the evaporator core is
allowed to warm up during "OFF" cycles. The
temperature control thermostat cuts out at 32°F.,
"Hornet" and "Wasp" Series, and 34°F. on the
"Rambler" Series as sensed by the capillary tube.
The thermostat points are opened and current to
the solenoid by-pass valve is closed off. This de-
energizes the solenoid by-pass valve and the
by-pass circuit is open.
High pressure refrigerant vapor from the
compressor passes through the discharge service
valve through the line to the condenser. From the
condenser it is directed from the by-pass line to
the solenoid by-pass valve. From the solenoid
by-pass line, it passes through a line that is
connected by a "T" connection to the suction line
in the "Hornet" and "Wasp" Series and the suction