LG LMVH1750SB Service Manual page 31

(2)CHECKOUT PROCEDURES FOR RELAY.
-PROBLEM (A)-
FAN motor turns on without touching START/ENTER
key when the door is closed.
NO
Remove the mate connector of I/O
GOOD
CON from the circuit board.
Does the unit still operate?
Replace the
circuit board
-PROBLEM (B)-
FAN motor turns on When the door is closed and
START/ENTER key is touched.
YES
Measure the voltage at pin NO.
GOOD
1,10 of CN1
Voltage reading:120 V AC
Replace the
circuit board
YES
NO
Defective
Wire Assembly
Replace
Wire Assembly
NO
NO
Defective
FAN motor
Replace
FAN motor.
Oven lamp turns on without touching START/ENTER
NO
GOOD
YES
Oven lamp turns on When the door is closed and
YES
GOOD
YES
7-21
-PROBLEM (A)--
key when the door is closed.
Remove the mate connector of I/O
CON from the circuit board.
Does the unit still operate?
NO
Replace the
circuit board
-PROBLEM (B)-
START/ENTER key is touched.
Measure the voltage at pin NO.
1,10 of CN1
Voltage reading:120 V AC
NO
Replace the
circuit board
YES
YES
Defective
Wire Assembly
Replace
Wire Assembly
NO
YES
Defective
Oven lamp
Replace
Oven lamp