Interlock Continuity Test - LG MH-1355M Service Manual

INTERLOCK CONTINUITY TEST

• The service personnel should replace all of the monitored safety interlock switches and monitor switch if the
oven has been rendered inoperative due to the failure of the monitored safety interlock(s).
• Be sure to connect the monitor switch after replacement and to check interlock/monitor continuity.
COMPONENTS
SWITCHES
(Wire leads removed)
PRIMARY INTERLOCK (UPPER LATCH)
SWITCH TEST
When the door button is slowly depressed with the
door closed, an audible "click" should be heard at
the same time or successively at intervals. When the
button is slowly released, the latches should activate
the switches with an audible "click".
If the latches do not activate the switches when the
door is closed, the switches should be adjusted in
accordance with adjustment procedure.
Isolate the primary switch by disconnecting it from
leadwire. Connect the ohmmeter leads to the common
(COM) and normally open (NO) terminal of the switch.
The meter should indicate an open circuit in door
open condition.
When the door is closed, the meter should indicate a
closed circuit.
When the primary switch operation is abnormal, make
the necessary adjustment or replace the switch only
with the same type of switch.
TEST PROCEDURE
Check for continuity of the switch
with an Ohm-meter
Primary
Switch
Monitor
Switch
Secondary
Switch
NOTE : After checking for the continuity of switches, make sure the wires are
correctly connected.
NO
COM
NC
COM
NO
COM
SECONDARY INTERLOCK (LOWER
LATCH) SWITCH TEST
Isolate the secondary switch by disconnecting it from
leadwire. Connect the ohmmeter leads to the common
(COM) and normally open (NO) terminals of the
switch. The meter should indicate a closed circuit in
the door open condition. When door is closed, the
meter should indicate an open circuit. When the
secondary switch operation is abnormal, make the
necessary adjustment or replace the switch only with
the same type of switch.
MONITOR SWITCH TEST
Isolate the monitor switch by disconnecting it from
leadwire. Connect the ohmmeter leads to the common
(COM) and normally closed (NC) terminals of the
switch. The meter should indicate a closed circuit in
the door open condition. When door is closed, the
meter should indicate an open circuit.
When the monitor switch operation is abnormal,
replace the same type of switch.
NOTE: After repairing the door or the interlock
system, it is necessary to do this continuity test before
operating the oven.
– 25 –
RESULTS
Door Door
open closed