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compartment vent is located on the left side
as you view the front of the machine.
WATER LEVEL CONTROL
Water level is determined by air pressure
inside the line that is connected to the air
dome and transducer {PS2) on the control
board. This line consists of two rubber hoses
that are joined together with clamps and a
plastic nipple at the air dome. One end of air
dome connects to a nipple fitting on the drain
valve assembly. The opposite end of the line
connects to the nipple fitting of the trans-
ducer on the MKllA-20 control board.
When the machine is empty, the air dome
and line contain air at normal atmospheric
pressure. When the machine closes the drain
and fills with water, water enters the base of
the air dome and traps the air inside, pre-
venting it from escaping. As the water level
increases inside the tub of the machine, so
does the pressure on the air trapped inside
the air dome and line connected to the
transducer on the computer. When the
pressure is sufficient on the transducer
{according to the water level chosen by
programming of the control board) the
control board senses the machine is filled to
proper level and stops filling the machine.
In a drain step, the drain valve is opened by
the control board and water runs through the
drain to the sewer system. As the water level
drops in the machine, so does the pressure
on the air trapped inside the air dome and
line. Eventually the water level will drop low
enough that the water will drain out the base
of the air dome and the pressure will drop
low enough in the air line {and thus likewise
on the transducer) for the control board to
recognize that the machine is empty.
When installing a new machine, or new
control board, the
"O
level" must be set
using the "Initialization Procedure" for the
computer. For further information about
setting
"O
level", consult the Programming
and Operating Manual.
INLET VALVES
The various models are provided with differ-
ent sizes of inlet valves. However, the princi-
pal operation of these valves is the same
(See Figure 2-5). In clean water, the valve will
work problem free.
OPEN
CLOSED
E
F
Figure2-5
The water valves used on all models are
designed to operate within a pressure
range (of 30 lbs to 120 lbs).
The water at the inlet (G) is pushing against
the diaphragm (H). The solenoid plunger (8)
and the spring (A) by themselves are not
strong enough to keep the water pressure
from raising the diaphragm. Therefore, it is
necessary to equalize this pressure on both
sides of the diaphragm in order to keep the
diaphragm in a closed position. The flow of
water is blocked until the solenoid is ener-
gized.
To do this, a small pilot hole (C) is provided
in the diaphragm to allow water to flow into
the plunger area. The water in the plunger
area equalizes the pressure on both sides of
the diaphragm. The spring pushes the
plunger down into the center hole (D) of the
diaphragm and closes it until the solenoid is
energized. When the machine is in the fill
positions of the cycle, the solenoid is ener-
gized (see previous figure), creating an
electromagnetic field which pulls the plunger
{b) away from the center hole of the dia-
phragm. This allows water to escape
through the center hole in the diaphragm,
16009607
Section 2. Service Procedures
©1999 Maytag Appliances Sales Company
2-7
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