8
16022842 Rev. 0
©2003 Maytag Appliances Company
General Information
HOW IT WORKS
The cycles are made up of three basic operations Fill,
agitate and drain/spin. These operations are sequenced
by the controls (timer or microprocessor board) to provide
a proper cleaning cycle for each of several different
fabrics.
FILL
Pressurized hot and cold water supplies are required.
The dynamic, or flow pressure should be between 30 lbs.
per square inch and 80 lbs. per square inch (p.s.i.).
Pressure below 20 lbs p.s.i. may cause water line
hammering.
Hot water is describe to be 140° F and cold water
temperature should be 75° F. A 50-50 mix of hot water
and cold should result in warm temperature between
100° F and 105° F.
The components involved in a fill operation are the water
valve assembly, the water level control and the timer or
control board. The control board or timer along with the
selector switch tell the valve whether to allow hot, cold or
both (warm) into the washer. The water level control
(a.k.a. pressure switch) controls the level of the water in
the washer. It should be at the top row of holes
(perforations) in the washer basket plus or minus 1/4 inch.
Water Valve (Non-Thermostatic)
The water valve used on the top load washers is designed
to operate with in a pressure range of 30-120 p.s.i.. Flow
pressure cannot fall below 20 p.s.i. or valves may fail to
close when solenoids are de-energized.
Water from source enters valve at inlet and pushes up on
diaphragm. The solenoid plunger and the plunger spring
are not strong enough to hold the diaphragm in a closed
position. The diaphragm lifted and some water will flow
under the diaphragm and into the outlet.
Some water also flows through bleeder holes in the
diaphragm and into the guide tube area behind the
diaphragm. With the solenoid not energized, the plunger
would block the pressure release hole allowing the guide
tube to pressurize to source pressure. This causes the
diaphragm to be pushed against the valve seat blocking
the valve seat and closing the outlet.
While there is equal pressure (source pressure) on both
sides of the diaphragm, the pressure in the guide tube
area covers a greater surface area of the diaphragm. The
center (outlet area) on the bottom side of the diaphragm is
at atmospheric pressure so the valve remains closed. It
is important to understand that water pressure is the
operation force in the water valve.
When the valve operating solenoid is energized, a
magnetic field is produced that lifts the plunger away from
the pressure release hole in the center of the diaphragm.
The pressure in the guide tube area is released through
the hole allowing the inlet pressure to lift the diaphragm off
of the outlet seat. Water flows under the diaphragm and
out through the valve outlet.
Because the bleed holes cannot allow water into the
guide tube area as rapidly as it can escape out through
the pressure release hole, the diaphragm will remain in
the open position as long as the plunger is held away
from the release hole.
When the plunger is released (solenoid coil de-energized),
it again blocks the release hole allowing pressure entering
though the bleed holes to again force the diaphragm back
against the outlet seat, stopping the flow of water. A
nozzle arrangement at the center of the diaphragm
causes the valve closure to be gradual and smooth to
reduce the chances of water hammer as the valve closes.
Water Level Control (Pressure Switch)
The water level switch is a single pole-double throw switch
which is activated by air pressure increase against a
sealed diaphragm. An air hose is connected to a spout at
the bottom of the outer water container (outer tub) and to
an inlet spout at the water level control body.
As water enters the tubs and the water level raises, air is
trapped in the air dome at the bottom of the pressure
switch hoses. As the water level increases, this air is
pushed up the hose and against the diaphragm in the
water level control body.
The control is designed to cause the contact points to
switch when the water level in the wash basket (and the
outer container) reach a particular level. At that point the
fill circuits are disconnected and the motor circuit is
energized. This corresponds to empty = fill and full = run.
Air leaks at the hose connections cannot be tolerated for
proper operation of the water level control.
In timer models, a bypass circuit is provided by the timer
and selector switch to continue power to the motor in spin
operations. Without the bypass, the drive motor would
stop when sufficient water had been pumped out of the
washbasket to cause the pressure switch to reset to the
”empty” position. Microprocessor models do not need the
bypass circuit.
