Chevrolet 1977 light duty truck Service Manual page 57

To employ our tire pu m p analogy once more for
clarity, it is the same situation that would exist if you
were inflating a tire with a very slow leak. Providing you
pu m p ed the air into the tire as fast as it leaked out. you
would be able to m aintain pressure even though the air
would merely be circulating through the tire and leaking
out through the puncture.
A ccum u lato r-C -K M odels (Fig. IB -8 )
T he accumulator is located at the evaporator outlet.
Its most im p ortant function is not to "accum ulate"
although this too is im portant. Its prim ary function is to
separate liquid retained from vapor, retain the liquid
and release the vapor to the compressor.
Thus, in and ideal accumulator with no oil bleed
hole, an d in a correctly designed system, no liquid can
get to the compressor.
In an actual accumulator, there is some entrained
liquid in the vapor stream to the compressor. The
measure o f a good accumulator is how well it separates
vapor from liquid and how little entrained liquid is
released to the com pressor.
accumulator, an oil bleed hole is required to prevent
trap ping o f oil in the bottom o f the accumulator; this oil
bleed hole bleeds some liquid refrigerant as well.
Also, in an actual
Therefore, flow out o f the accumulator to the
compressor consists mostly of vapor with the addition of
entrained liquid and liquid flow through the oil bleed
hole.
A bag o f desiccant (dehydrating agent) is located in
the base of the accumulator as a moisture collecting
device.
N OTE: There is no sight glass in the accumulator-
clutch cycle system.
Expansion T ube-C -K Models
Expansion tube flow rate depends on
difference and on subcooling; however, the flow rate is
more sensitive to subcooling.
The expansion tube is located in the evaporator inlet
line (fig. IB-9).
Therm ostatic Switch
System tem perature is controlled by running the
compressor intermittently, automatically turning it on
and off as necessary to m aintain proper temperatures.
The compressor is started and stopped through the use o f
an electro-magnetic clutch and a thermostat affected by
variations in temperature.
The thermostatic switch incorporates a metallic tube
which contains a highly expansive gas. This tube is
inserted into the evaporator inlet line (C-K Four-Season
System) or is located in the air stream as it leaves the
evaporator (Motor Home Chassis Unit). The tube leads
to a bellows operated switch. As air tempeature rises, the
gas inside the tube expands, travels through the tube to
the bellows and closes the electrical switch which engages
the compressor clutch.
As soon as the compressor starts running, the
tem perature begins to go down. As the air being cooled
gets colder, the gas in the thermostatic tube begins to
reduce the pressure on the switch bellows. This allows the
pressure
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