Service manual

41
When warm or hot temperature is selected, the control
board connects the hot water solenoid to neutral and
cycles the cold water solenoid off and on to regulated
the temperature. When cold temperature is selected,
the control board connects the cold water solenoid to
neutral and cycles the hot water solenoid off and on to
regulated the temperature.
Water Inlet Valve
The water valve is mounted to the rear rail under the
main top in the lefthand corner.
The water inlet valve is actually two solenoid operating
valves in one body. A hot water valve and a cold water
valve discharge into a common mixing chamber. The flow
of water out of the chamber is controlled by a molded in
flow washer capable of maintaining a flow rate of 3.0 -
14.6 gallons per minute, with incoming water pressure of
30 to 120 P.S.I. The inlet valve is controlled by the control
board individually or together, to provide hot, cold, or
warm water for washing and cold or warm water for
rinsing.
Valve Operation
Both inlet solenoid valves are identical in construction
and operation. The valve body provides an air passage
with a large orifice and seat where the water can be
stopped. The outlet of the valve body empties into the
mixing chamber. A moveable rubber diaphragm operates
against the valve seat to start and stop the flow of water.
The diaphragm is operated by water pressure. It has a
small bleed orifice outside the seat contact area, and a
large main orifice at its center. The armature of the
solenoid serves to open and close the main orifice. The
armature operates within a closed metal tube (valve
guide) which is sealed by the outer edge of the
diaphragm to the valve body. A coil spring holds the
armature down against the diaphragm main orifice when
the solenoid is not energized.
The following line drawings and text explains basic valve
operation.
When the valve is in a closed position, the solenoid is not
energized. Water has bled through the diaphragm bleed
orifice placing incoming line pressure on top of the
diaphragm. The bottom of the diaphragm is essentially at
atmospheric pressure (open to the outlet) and the
pressure differential holds the valve shut.
Water Valve Closed
When the solenoid is energized, the resulting magnetic
field pulls the armature up into the valve guide.
The armature spring is compressed by this action. When
the armature moves up, it allows the water on the top of
the diaphragm to drain through the main orifice.
The diaphragm bleed orifice is much smaller than the
main orifice and will not admit enough water to maintain
pressure on the top side of the diaphragm. Thus, as the
pressure on the top of the diaphragm is reduced to
almost zero, the pressure on the bottom lifts the
diaphragm off the valve seat, allowing a full flow of water.
Solenoid Activated