GMC 1976 ZEO 6083 Maintenance Manual page 60

RECEIVER-DEHYDRATOR
The receiver-dehydrator (figures 13 and 14),
sometimes called the receiver-drier or just drier, is so
called because of its function of receiving liquid re
frigerant from the condenser and, by means of a
dehydrating agent, removes any water present from
it. This chemical compound is called a desiccant. The
desiccant is held in place in a felt bag in the drier.
Average receiver-drier desiccants collect and hold
about 50 drops of water. This may not seem like
much until you realize that one drop of water can
block the whole air conditioning system .
The drier also filter-traps any foreign matter
which may have entered the system during assembly
or during any service work . This is accomplished by
means of a fine wire screen .
Still another function of the receiver dehydrator
is to act as a reservoir to furnish a constant column
Figure 15-Evaporator Housing Components, Type 1
AIR CONDITIONING SYSTEM
1- 43
of liquid refrigerant to the expansion. valve at all
times. Since the entering liquid refrigerant may have
some gas in it, the tank acts as a separator . The gas
will tend to rise and the liquid will drop to the bot-
tom. This is why the pick-up tube extends to the
bottom of the tank insuring gas free liquid R-12 to
the expansion valve. The storage of the refrigerant is
temporary, and is dependent on the demand placed
on it by the expansion valve .
While having no real function to perform in the
system, the sight glass is a valuable aid in determin-
ing whether or not the refrigerant charge is sufficient
and for eliminating some guess work in diagnosing
difficulties . The sight glass, is built into the receiver-
dehydrator outlet connection and is designed and
located so that a shortage of refrigerant at this point
will be indicated by the appearance of bubbles
beneath the glass. The dust cap provided should be
kept in place when the sight glass is not in use.
THERMOSTATIC SWITCH