Chevrolet 1977 light duty truck, Руководство по обслуживанию

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T o employ our tire p u m p analogy once more for
clarity, it is the same situation th at would exist if you
were inflating a tire with a very slow leak. Providing you
p u m p e d the air into the tire as fast as it leaked out. you
would be able to m ain tain pressure even though the air
would merely be circulating through the tire and leaking
out through the puncture.
A ccu m u lato r-C -K M odels (Fig. IB -8 )
T h e accum ulator is located at the e v ap o rato r outlet.
Its most im p o rta n t function is not to " a ccu m u late"
although this too is im portant. Its prim ary function is to
sep arate liquid retained from vapor, retain the liquid
and release the v apor to the compressor.
Thus, in and ideal accum ulator 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 vap o r stream to the compressor. The
m easure o f a good accumulator is how well it separates
v a p o r from liquid and how little en train ed liquid is
re le a se d
to the c om pressor. Also, in an actual
accumulator, an oil bleed hole is required to prevent
tra p p in g o f oil in the bottom o f the accumulator; this oil
bleed hole bleeds some liquid re frig e ran t as well.
Therefore, flow out o f the accum ulator to the
compressor consists mostly o f vapor with the addition o f
entrained liquid and liquid flow through the oil bleed
hole.
A bag o f desiccant (dehydrating agent) is located in
the base o f the accumulator as a moisture collecting
device.
N O TE: There is no sight glass in the accumulator-
clutch cycle system.
Expansion T u b e-C -K M odels
Expansion tube flow rate depends on pressure
difference and on subcooling; however, the flow rate is
more sensitive to subcooling.
The expansion tube is located in the e v ap o rato r inlet
line (fig. IB-9).
Therm o static Switch
System tem p eratu re is controlled by run n in g the
compressor intermittently, automatically turning it on
and off as necessary to m ain tain proper temperatures.
T he compressor is started and stopped through the use o f
an electro-magnetic clutch and a therm ostat affected by
variations in tem perature.
The thermostatic switch incorporates a metallic tube
which contains a highly expansive gas. This tube is
inserted into the evap o rato r inlet line (C-K Four-Season
System) or is located in the air stream as it leaves the
evaporator (M otor Home Chassis Unit). The tube leads
to a bellows operated switch. As air tem peature 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
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