GMC 1986 P-Truck Service Manual page 67

1B-4 AIR CONDITIONING
C
A. Inlet
B. Outlet
C. Refrigerant Vapor Outlet
15. Baffle
16. Internal Tube
17. Desiccant Bag Assembly
18. Filter Assembly
19. Oil Bleed Hole
Figure 2—Accum ulator C-K & G Series
SYSTEM COMPONENTS
THERMOSTATIC EXPANSION VALVE
Suburban and G rear interior roof mounted and
motor home chassis systems use a thermostatic ex­
pansion valve (figure 1).
The valve consists of the power element, body,
actuating pins, seat and orifice. At the high pressure
liquid inlet, a fine mesh screen prevents dirt, filings or
other foreign matter from entering the valve orifice.
When the valve is connected in the system, high
pressure liquid refrigerant enters the valve through the
screen from the receiver-dehydrator or condenser and
B
A. Inlet (R-12 From Condenser)
B. Outlet (To Evaporator)
D. Dent In Tube (Retains The Expansion Tube)
F-00191
25
—— = — I
/-T.. . . ..-........... 1
| §
Figure 3—Orifice (Expansion Tube)
passes on to the seat and orifice where it changes into
a low pressure liquid.
The low pressure liquid leaves the valve and flows
into the evaporator core where it absorbs heat from the
evaporator core and changes to a low pressure vapor
and leaves the evaporator core. The power element
bulb is clamped to the low pressure vapor line just
beyond the outlet of the evaporator.
ACCUMULATOR C-K & G SERIES
The accumulator is located at the evaporator outlet.
It separates liquid retained from vapor, retains the
liquid and releases the vapor to the compressor (figure
2
).
Flow from the accum ulator to the compressor
consists of vapor, entrained liquid and liquid flow
through the oil bleed hole.
A bag of desiccant (dehydrating agent), located in
the accumulator, collects moisture.
There is no sight glass in the accumulator with the
CCOT system.
ORIFICE (EXPANSION TUBE) C-K & G SERIES
Pressure differences and sub-cooling determines
expansion tube flow. The orifice is located in the
evaporator inlet line (figure 3).
PRESSURE CYCLING SWITCH
This switch controls evaporator temperature. It
cycles the compressor clutch off when the evaporator
temperature gets too low. It cycles the compressor
back on after evaporator temperature has increased
(figure 4).
The cycling pressure switch provides inherent
compressor protection so a separate low pressure
switch is not necessary. The switch also acts as an
ambient switch since at ambient freezing temperatures
it will not allow the compressor to engage. Adjusting
the set screw one-half turn left or right will rise or lower
the settings 20.7 kPa (3 psi) (figure 5).
26
--------------
IW 1
j j ||j n . _ _ _
L _ Z . □
1
— __— .
28
25. Outlet Screen
26. Expansion Tube
27
J-
i n I
sia5=j i |
27. Inlet Screen
28. Seal (O Ring)
F-00192