Section 22: HEATING AND AIR CONDITIONING
PA1562
26
2. Take out the retaining screw at the top of
the coil housing. The entire coil assembly
can then be lifted off the enclosing tube.
3. Place the new coil and yoke assembly on
the enclosing tube. Lay data identification
plate in place.
4. Insert the coil retaining screw, rotate
housing to proper position and tighten screw
securely.
5. Connect connector from coil connector.
7.7.3 Valve Disassembly
1. Remove the coil as stated previously.
2. Pump down the system as stated earlier in
this section.
3. Remove the four socket head screws which
hold the body and bonnet together (Fig. 31).
4. Carefully lift off the bonnet assembly (upper
part of the valve) so that plunger will not fall
out. The diaphragm can now be lifted out.
NOTE
The above procedure must be followed before
brazing solder-type bodies into the line.
CAUTION
Be careful not to damage the machined faces
while the valve is apart.
7.7.4 Valve Reassembly
1. Place the diaphragm in the body with the
pilot port extension up.
2. Hold the plunger with the synthetic seat
against the pilot port.
3. Make sure the bonnet O-rings are in place.
Lower the bonnet assembly over the
plunger, making sure that the locating
sleeve in the bonnet enters the mating hole
in the body.
4. Insert the four socket head screws and
tighten evenly.
5. Replace the coil as stated previously.
6. Add a small quantity of refrigerant R-134a to
the low side of the system. Check for leaks.
Return the system to normal operation.
FIGURE 31: REFRIGERANT SOLENOID VALVE 22044
7.8 EXPANSION VALVE
The expansion valve for the central system is a
thermo-sensitive valve with a remote control
bulb head attached to the evaporator outlet line
and is accessible by the evaporator coil access
door (Fig. 14 & 32). The valve regulates the flow
of refrigerant liquid into the evaporator coils and
is controlled by the suction gas temperature
leaving the evaporator. The bulb head senses
the refrigerant gas temperature as it leaves the
evaporator. High temperature will cause
expansion and pressure on the power head and
spring. Such action causes the assembly valve
to open, allowing a flow of refrigerant liquid into
the evaporator.
The remote bulb and power assembly is a
closed system. The pressure within the remote
bulb and power assembly corresponds to the
saturation pressure of the refrigerant
temperature leaving the evaporator and moves
the valve pin in the opening direction. Opposed
to this force, on the under side of the diaphragm
and acting in the closing direction, is the force
exerted by the superheat spring. As the
temperature of the refrigerant gas at the
evaporator outlet increases above the saturation
temperature corresponding to the evaporator
pressure, it becomes superheated. The
pressure thus generated in the remote bulb and
power assembly surpasses the combined
pressures of the evaporator pressure and the
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