Figure 5-27.A typical automatic residential washer.
direction the drive motor spins. Whenever the drive
motor turns in one particular direction, the
transmission is shifted to the spin gear. Reversing the
motor then automatically shifts the transmission to its
Some washing machine transmissions also have a
neutral gear that allows the drive motor to turn without
causing either the spin or agitation action to occur.
This feature is used during drain operations that call for
running the water pump by itself.
MAIN DRIVE MOTOR.The main drive
motor is responsible for converting electrical energy
into the kind of mechanical power that is necessary for
carrying out the agitation, spin, and pumping actions of
the washer. The motor is normally a split-phase
induction motor that is rated at about one-half
horsepower. Washer motors, almost without
exception, operate on 120-volt line power.
A capacitor-start feature is not necessary for
washing machines using fractional horsepower drive
motors, but a centrifugal switch or relay-start
mechanism is always an integral part of the control
system of the main drive motor. In some cases, you
will find that washer motors are also reversible and
they sometimes have built-in speed control windings.
WATER PUMP ASSEMBLY.The primary
purpose of the water pump is to draw used water out of
the washer at the end of the washing and rinsing steps
and during spin operations. The pump is also used to
recirculate the wash and rinse water with the use of a
lint filter. The water pump is mechanically driven by
the transmission and main drive motor and is operating
anytime the main drive motor is running. Consider
now the fact that the main drive motor is reversible in
most models. It runs in one direction for agitation
operations and in the opposite direction for spin
operations. This means the water pump runs in both
directions as well; and the logical conclusion is the
pump moves water in two different directions,
depending on which way the main drive motor is
It is possible to take advantage of this two-
direction characteristic of the water pump by using it in
conjunction with a two-way flapper-valve assembly.
The idea is to recirculate the wash or rinse water during
agitation operations and to pump the water out of the
system during spin operations. By turning the drive
motor and pump in the agitation direction (fig. 5-28,
view A), valve A is opened and valve B is closed. The
water is thus routed through the water recirculation
system inside the machine. By turning the drive motor
and pump in the spin direction (fig. 5-28, view B),
valve A is closed and valve B is opened. Since valve B
leads to the wastewater system, moving the water in
that direction effectively drains it all out of the washer.
This makes it possible to use a flapper-valve assembly
for routing the water without using extra electrical
controls and timer switches. Some washers control the
routing of the pump water by means of solenoid valves.
Figure 5-28.Operation of a flapper-valve water control
system: A. Pump turning in the agitate direction to
recirculate the water; B. Pump turning in the spin
direction to pump water out of the washer.