Door Lock Operation - Maytag MFR Series Service Manual

The MFR line of commercial washer models
use an electro-mechanical door lock assembly
mounted to the outer tub front at the 9:00
o'clock position. The door handle lever
"pivots" into and around a roller/pin in the door
lock casting and lifts a door lock leaf-spring
as the handle is latched. Unless and until this
leaf-spring is moved forward the door locking
solenoid cannot move the door lock latch bar
behind the door handle lever end to lock the
door.
As the door is closed an alignment pin on
the door ring lines up with and enters into a
socket located just below the door lock roller
pin. This alignment pin presses on the leaf
of the door closed switch to close the door
switch contacts. At this point the main control
board "knows" the door is closed. When the
vend price is satisfied and a cycle selection
button is pressed in the MFRxxPDC washers;
or a cycle selection is made and the start pad
is pressed in the MFRxxPNC washers, the
main control will activate the relay for the door
lock solenoid bridge rectifier (located on the
control board). This provides a DC voltage
of about 200VDC to the door lock solenoid
coil. The door lock coil is the horizontally
mounted solenoid. The solenoid armature
will push the door lock latch bar to the right
behind the door handle lever tongue blocking
the lever in the door-locked position. As the
latch bar moves to the right, the roller of the
door locked switch follows the horizontal
ledge of the latch bar and changes the switch
contacts from the "open" position to the "door
locked" position. With the closure of the "door
locked switch" the selected cycle will start.
Several things happen at once; the drain valve
motor is powered to close the drain valve,
the appropriate fill valve solenoid coils are
powered to begin the filling process, the motor
starts to turn the inner basket, and the display
will indicate the cycle has begun.

DOOR lOCk OpeRaTiOn

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At the beginning of the cycle, power is also
provided to the door lock bi-metal latch in
the door lock assembly. Within about twenty
seconds the internal heater will cause the
bimetal bar in the latch to bend and lower a
"blocking bar" behind the armature of the door
lock solenoid to block it in the door locked
position. This blocking bar will keep the
solenoid armature pushed over to the right,
which keeps the latch bar behind the door
handle lever so in effect the door cannot be
opened.
At about 90 seconds to two minutes after
a start, power to the door lock solenoid is
removed for about ten seconds as a "check" to
see that the blocking bar was in fact activated
by the bi-metal latch. It is important that this
bi-metal latch and blocking bar function as
a safety to keep the door locked for a "coast
down" period in case of a power failure during
a spin step. The bi-metal latch will cool on
loss of power in about 30 to 40 seconds and
lift the blocking bar from behind the door lock
solenoid armature. At that point the door
lock will be released. If the bi-metal does not
function as designed during the safety check
period, the washer will stop and an error
message will be posted in the display.
Unlocking the door:
A separate DC solenoid (door release
solenoid) is used to push the blocking bar
back up from behind the door lock solenoid
armature. This is the vertical mounted
solenoid. Presuming the door lock solenoid is
not powered (as would be the case at the end
of a cycle), pushing the blocking bar back up
would allow the lock solenoid armature (and
latch bar) to move back to the left. (There is
a small coil spring on the latch bar to pull it
back to the left)