LG LMVM1935SB Service Manual page 31

(2) CHECKOUT PROCEDURES FOR RELAY.
FAN motor and oven lamp turn on without touching
START key when the door is closed.
NO
GOOD
Replace the
circuit board
- PROBLEM (A) -
YES
Remove the mate connector of I/O
CON from the circuit board.
Does the unit still operate?
NO
Defective
RELAY1
YES
Replace
RELAY1
FAN motor and oven lamp turn on When the door is
closed and START key is touched.
YES
GOOD
7-19
- PROBLEM (B) -
NO
Measure the voltage at pin NO.
35 of U01
Voltage reading: 0 Vdc
10 of U03
Voltage reading: about 15V
NO
Replace the RELAY1 or poor
circuit board
RELAY1 or correct
YES
Defective
connection of
RELAY1
Replace
the connection.