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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 fuse F2 (F8A) in the monitored latch switch - monitor switch
circuit, check the monitored latch switch and monitor switch before replacing the fuse F2 (F8A).
FAN MOTOR FM
The 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 vapours given off
from heating food. It is then exhausted through the exhausting air
vents of the oven cavity.
CONVECTION MOTOR CM
The convection motor drives the convection fan and provides the
heated air.
TOP GRILL HEATING ELEMENT GH1
The grill heating element is provided to brown the food and is
located on the top of the oven cavity.
BOTTOM GRILL HEATING ELEMENT GH2
The grill heating element is provided to brown the food and is
located at the base of the oven cavity.
CONVECTION COOKING SYSTEM
This oven is designed with a hot air heating system where food
is heated by forced circulation of the hot air produced by the grill
heating elements.
The air heated by the grill heating elements is circulated through
the convection passage provided on the outer casing of the oven
cavity by means of the convection fan which is driven by the
convection motor. It is then enters the inside of the oven through
the vent holes provided on the back side of the oven. Next, the
hot air heats the food on the turntable and leaves the oven cavity
through the vent in the oven cavity rear wall.
In this way, the hot air circulates inside the oven cavity to raise
its temperature and, at the same time, comes into contact with
the food being cooked.
When the temperature inside the oven cavity reaches the se-
lected temperature, the heating elements are de-energized.
When the temperature inside the oven cavity drops below the
selected temperature, the heating elements are energized again.
In this way, the inside of the oven cavity is maintained at
approximately the selected temperature.
When the convection time reaches “0”, the heating elements are
de-energized and the convection fan stops operating and the
oven shuts off. At that time if the cavity air temperature has rised
above120
˚
C, the fan motor remains rotating. Automatically the
fan motor will be shut down at low temperature (less than 105
˚
C).
Door
Oven Cavity
Grill Heating
Element
Bottom Grill
Heating Element
Convection
Passage
Cooling
Fan
Convection
Motor
Convection
Fan
Turntable
Insulation
Turntable
Motor
FUNCTION OF IMPORTANT COMPONENTS
FIRE SENSING FEATURE
The oven will stop its operation when there is a fire in the oven
cavity in microwave cooking condition.
LSI measures the voltage across the temperature measurement
circuit intermittently within 32-seconds time base since the oven
is started in microwave cooking condition. The oven will stop its
operation when the difference of the voltage is more than 0.781
volts in microwave cooking condition.
1. Within a 32-seconds base, the thermistor is energized for 2
seconds. At that time, the voltage across the temperature
measurement circuit is measured.
2. The oven carries out the procedure above again. If the
second voltage is 0.781V higher than first voltage, LSI judges
it as a fire in the oven cavity and stop the oven.
3. When LSI judges it as a fire in the oven cavity, LSI will switch
off the relays to high voltage transformer and fan motor and
LSI stops countring down.
Figure D-2. Convection Cooking Syste
OPEN JUDGE BY THERMISTOR
1. If the temperature of the thermistor does not rise to
more than 40
˚
C after 4 minutes and 15 seconds from
when the oven is started in convection, grill (top and
bottom grills) or dual cooking mode, the oven is turned
off.
2. When the thermistor or the wire harness to the thermis-
tor is opened, the oven is turned off after 4 minutes and
15 seconds because this condition is same as above.
THERMISTOR
SENSING
VOLTAGE
ON
OFF
ON
OFF
30
32 (sec.)
Sensing the voltage across temperature measurement circuit.
