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section.)
SERVICE INSTRUCTIONS
4.
Test
for
pilot
pressure.
See
Service
Instruction "J", Pilot Pressure System.
5.
If 12-15 VDC is measured
at connecting
leads to four-way
and
pilot pressure is
normal
then
four-way
valve
is either
defective or foreign
matter
has gotten
inside valve causing it to malfunction. In
either case the four-way valve must be
removed to clean or replace it.
To remove four-way valve:
1.
Unplug unit from wall outlet.
2.
Refer to Service Instruction
B to open
front cover.
3.
Disconnect the two wires from terminals
on pilot valve (14 Fig. 16).
4.
Remove the pilot pressure tubing from
pilot valve (13 Fig. 16).
5.
Remove the two allen head cap screws (2
Fig. 16) from top of four-way
using an
allen wrench. The top or valve body and
gasket can now be removed.
NOTE:
Do
not
remove
manifold.
The
manifold will remain on the unit whether you
are cleaning or replacing the valve.
To clean the four-way valve:
1.
Remove the two allen head screws from
the top of four-way valve. The top or the
valve body can now be removed
along
with the pilot valve. The valve manifold
will remain on the unit. A rubber gasket
located between the valve body and valve
manifold should also be removed.
2.
Remove the 4 screws from the ends of the
valve
so that the
end
plates,
plastic
spacers and spring can be removed. Note
position of these parts.
3.
Carefully remove spool from valve body.
Using a non-metallic rod or dowel with a
diameter
no greater than the sleeve,
slowly push the sleeve out either end of
the valve body.
(Note:
Pushing
too fast
will
cause
o-rings
to
roll and
jam).
Remove the "O" rings from the sleeve and
inspect them for signs of damage. If they
are damaged,
they should
be replaced
using valve rebuild Kit #MC44D-707 prior
to reinstallation of the sleeve into the
valve body.
5.
Wash the spool and sleeve (less "O" rings)
in warm,
soapy water
until
all of the
17
deposits have been removed. The plastic
spacers and spring may also be cleaned if
needed. (Important: never try to scrape
the spool or sleeve or use an abrasive
substance
for cleaning.
This
would
adversely affect the operation
of the
valve).
6.
Rinse the spool and sleeve thoroughly
and dry with a soft, clean, lint-free cloth.
Reinstall or replace "0" rings on sleeve.
7.
Ensure that the air passages
(ports)
in
both the valve body and manifold are free
of any foreign matter. A ciean lint-free
cloth or a compressed
air hose can be
used to clean these.
8.
Carefully push sleeve
into valve
body
(turning it slightly) so you do not cut or
knick
the
o-rings.
To
ensure
proper
placement
of spool,
use white
plastic
spacer and push until spool is flush with
valve body.
9.
Reassemble remaining
parts of valve in
reverse order.
To replace four-way valve:
1.
Align valve body and gasket on manifold.
Ensure that gasket is aligned
properly.
Secure with two allen head screws.
2.
Attach
pilot pressure tubing
to pilot-
valve.
3.
Reconnect the two wires on terminals of
pilot valve.
4.
Replace the front cover and secure with
cabinet fasteners.
H. Purge Valve
Like
the
four-way,
the
pneumatically
operated
purge valve (13 Fig. 11) uses an
external
pilot valve. This pilot valve
will
receive a signal (approximately
12-15 VDC)
from the MC board at the beginning of each
cycle (except the first) causing the purge to be
activated
for approximately
1.0 seconds.
While
the
purge
is activated,
oxygen
is
transferred from the pressurized bed to the
depressurized
bed and the exhaust
port is
closed. When
the purge is deactivated
the
exhaust port opens allowing
nitrogen
to be
exhausted. It is released through a muffler (6
Fig. 19) located on the vertical divider behind
the compressor.
10/87
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