9
R-310AK
R-330AK
R-330AW
secondary interlock switch are in the OFF condition
(contacts open) due to their being normally open contact
switches.
2. As the door goes to a closed position, the monitor switch
contacts are first opened and then the door sensing
switch and the secondary interlock switch contacts close.
(On opening the door, each of these switches operate
inversely.)
3. If the door is opened, and the primary interlock relay and
secondary interlock switch contacts fail to open, the
monitor fuse blows simultaneously with closing of the
monitor switch contacts.
CAUTION: BEFORE REPLACING A BLOWN MONITOR
FUSE TEST THE DOOR SENSING SWITCH,
PRIMARY INTERLOCK RELAY, SECONDARY
INTERLOCK SWITCH AND MONITOR
SWITCH FOR PROPER OPERATION. (RE-
FER TO CHAPTER "TEST PROCEDURE").
NOTE: MONITOR FUSE AND MONITOR SWITCH ARE
REPLACED AS AN ASSEMBLY.
OUTER CASE SWITCHES (For the ovens from Oct.
1996 production)
The two outer case switches are mounted near the power
supply cord at the oven cavity rear plate. When the outer
case cabinet is installed with the screws, one of the screws
pushes the actuator and then the actuator pushes the two
plungers of outer case switches and their contacts are
closed. When a cabinet mounting screw which is pushing
the actuator is removed, the two outer case switches inter-
rupt the circuit to the all components.
OUTER CASE
CABINET
OUTER CASE
SWITCHES
ACTUATER
TURNTABLE MOTOR
The turntable motor rotates the turntable located on the
bottom of the oven cavity, so that the foods on the turntable
cook evenly during cooking. The turntable may turn in either
direction.
COOLING FAN MOTOR
The cooling fan motor drives a blade which draws external
cool air. This cool air is directed through the air vanes
surrounding the magnetron and cools the magnetron. This
air is channelled through the oven cavity to remove steam
and vapors given off from the heating foods. It is then
exhausted through the exhausting air vents at the oven
cavity.
MONITOR FUSE
1. The monitor fuse blows when the contacts (COM-NO) of
the primary interlock relay and secondary interlock switch
remain closed with the oven door open and when the
monitor switch closes.
2. If the wire harness or electrical components are short-
circuited, this monitor fuse blows to prevent an electric
shock or fire hazard.
OVEN THERMAL CUT-OUT
The thermal cut-out, located on the top of the oven cavity, is
designed to prevent damage to the oven by fire. If the foods
load is overcooked, by either error in cook time or defect in
the control unit, the thermal cut-out will open.
Under normal operation, the oven thermal cut-out remains
closed. However, when abnormally high temperatures are
reached within the oven cavity, the oven thermal cut-out will
open at 257˚F(125˚C), causing the oven to shut down.
MAGNETRON THERMAL CUT-OUT
The thermal cut-out located near the magnetron is designed
to prevent damage to the magnetron if an over heated
condition develops in the tube due to cooling fan failure,
obstructed air guide, dirty or blocked air intake, etc.
Under normal operation, the thermal cut-out remains closed.
However, when abnormally high temperatures are reached
within the magnetron, the thermal cut-out will open at
203˚F(95˚C) causing the oven to shut down, when the
magnetron has cooled to 167˚F (75˚C), the thermal cut-out
closes and cook cycle will resume.
This outer case mounting screw is push-
ing the actuator.
TROUBLESHOOTING GUIDE
When troubleshooting the microwave oven, it is helpful to follow the Sequence of Operation in performing the checks. Many
of the possible causes of trouble will require that a specific test be performed. These tests are given a procedure letter which
will be found in the "Test Procedure "section.
IMPORTANT: If the oven becomes inoperative because of a blown monitor fuse, check the monitor switch, primary interlock
relay, door sensing switch and secondary interlock switch before replacing the monitor fuse. If monitor fuse
is replaced, the monitor switch must also be replaced. Use part FFS-BA012WRK0 as an assembly.
