on the diaphragm which in turn permits a coil spring
to force the needle towards its seat. This action
reduces the liquid flow into the evaporator. The result
is a slowing up of the refrigerating action and a rise in
the temperature of the evaporator. See figure 5.
Fig. 5. Expansion Valve
From this it is obvious that if the expansion valve
should stick in either the open or closed position it
would cause a serious malfunction in the system. In
the open position, the valve would allow the Freon in
a liquid state to build up in the low pressure side.
Eventually this liquid could be pumped into the
compression chamber and rupture a head gasket, or
break the check valves in the compressor assembly.
In the closed position the expansion valve would
cause practically all the Freon to be "Pumped Down"
into the high pressure side of the system. In this state
no refrigeration could take place.
Fig. 6. The Receiver
A dehydrator is therefore placed in the liquid line to
remove small amounts of moisture that may have
been left in the system at the time of assembly. See
Fig. 7. The Dehydrator
Also required in this refrigeration system is a reservoir
or receiver. This unit receives the liquid refrigerant
from the condenser and also holds a reserve sup-ply
of fluid. See figure 6.
CAUTION: Extreme care should be used when
working on the refrigeration system to keep moisture
or moist air from entering the system.
Moisture is one of the enemies of a refrigerating
system. If even a trace of moisture circulates through
the system, it will materially reduce the life of the
compressor and in severe cases moisture will freeze
in the expansion valve and stop all refrigerating action.