R426LS
7 – 1
R426LS
Service Manual
CHAPTER 7.
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, relay (RY1) secondary interlock relay (RY2),
door sensing switch and primary interlock switch before replacing the
monitor fuse. If the monitor fuse is replaced, the monitor switch must
also be replaced. Use part FFS-BA033WRKZ or FFS-BA037WRKZ as
an assembly.
IMPORTANT
:
Whenever troubleshooting is performed with the power supply cord
disconnected. It may in, some cases, be necessary to connect the
power supply cord after the outer case has been removed, in this
event,
1) Disconnect the power supply cord, and then remove outer case.
2) Open the door and block it open.
3) Discharge high voltage capacitor.
4) Disconnect the leads to the primary of the power transformer.
5) Ensure that the leads remain isolated from other components and
oven chassis by using insulation tape.
6) After that procedure, reconnect the power supply cord.
When the testing is completed,
1) Disconnect the power supply cord, and then remove outer case.
2) Open the door and block it open.
3) Discharge high voltage capacitor.
4) Reconnect the leads to the primary of the power transformer.
5) Reinstall the outer case (cabinet).
6) Reconnect the power supply cord after the outer case is installed.
7) Run the oven and check all functions.
[1] TROUBLESHOOTING CHART
Never touch any part in the circuit with your hand or an uninsulated tool while the power supply is connected.
RE CK A B C D
E F F G H RE RE CK
J CK CK CK K L
N O
I
POSSIBLE CASE
AND DEFECTIVE PARTS
SHORT
IN
POWER
CORD
SHORT
OR
OPENED
WIRING
MAGNETRON
POWER
TRANSFORMER
H.V.
RECTIFIER
ASSEMBLY
HIGH
VOLTAGE
C
APACITOR
MAGNETRON
TEMPERATURE
FUSE
SECONDARY
INTERLOCK
SYSTEM
PRIMARY
INTERLOCK
SWITCH
MONITOR
SWITCH
MONITOR
FUSE
OVEN
LAMP
COOLING
FAN
MOTOR
TURNTABLE
MOTOR
TOUCH
CONTROL
PANEL
WRONG
OPERATION
LOW
VOLTAGE
DIRTY
OVEN
CAVITY
KEY
UNIT
(MEMBRAINE
S
WITCH)
RELAY
(RY1)
FOIL
PATTERN
ON
PWB
AH
SENSOR
NOISE
FILTER
CONDITION
PROBLEM
OFF
CONDITION
TTEST PROCEDURE
COOKING
CONDITION
SENSOR
COOKING
CONDITION
E
OVEN
THERMAL
CUT-OUT
M
DEFROST
Home fuse or circuit breaker blows when
power cord is plugged into wall receptacle
Monitor fuse blows when power cord is plug-
ged into wall receptacle.
All letters and indicators do not appear in dis-
play when power cord is first plugged into
wall outlet.
Display does not operate properly when
STOP/CLEAR pad is touched. (Buzzer
should sound and " : " or time of day
should appear in display.)
Oven lamp does not light when door is
opened.
Oven lamp does not go out when door is
closed.
Oven lamp lights but fan motor and turntable
motor do not operate.
Oven does not go into cook cycle when
START pad is touched
Oven seems to be operating but little or no
heat is produced in oven load. (Food incom-
pletely cooked or not cooked at all at end of
cook cycle.)
Oven goes into a cook cycle but extremely
uneven heating is produced in oven load
(food).
Oven does not cook properly when program-
med for Cooking Power P-50 mode. (Oper-
ates properly on Cooking Power P-HI (HIGH)
mode.)
Oven goes into DEFROST but food is not
defrosted well.
AH sensor does not end during Sensor cook-
ing condition. (Oven does not shut off after a
cup of water is boiling by sensor cooking.)
Oven stops at 16 sec. after starting.
