Test 4 Moisture Sensor - LG DLGX8001 Service Manual

Test 4
Moisture sensor
NOTE: This test has two parts. The best test of the moisture sensing system is done in the diagnostic mode. This
FUNCTIONAL TEST will test the sensor bars, wiring harness and PCB operation. If the results of this test are normal,
the sensor system and PCB response are normal. The problem is somewhere else.
FUNCTIONAL TEST (Control)
1. Enter the diagnostic mode. (See DIAGNOSTIC TEST MODE.)
2. With the door closed, press the START/PAUSE button once. The dryer will start tumbling without heat.
3. Open the door. The drum will stop tumbling and the "dE" error code will be displayed and the chime will sound several times (if turned on).
4. With one hand, reach into the drum and place your fingers across the moisture sensor bars.
(CAUTION: The dryer drum will turn in this test. Your hand will be close to the rotating drum vanes. Keep your hand close to the filter housing to
avoid being hit by the moving vanes.)
5. Use your other hand to press the door switch. The dryer drum will start rotating automatically.
6. Observe the numerical display. Depending on conditions, the number displayed should be between 30 and 255. The numbers should start
decreasing as the control senses the moisture in your skin.
7. After you have observed the number decreasing, remove your fingers from the sensor bars. The numbers will continue to decrease for a few
seconds (minimum 30) and the begin to increase (maximum 255).
8. If this test fails, proceed with the MECHANICAL TEST below.
Take NA8 Connector from
the controller.
Metal wire (Short)
Disconnect the NA8 connector from
the main PCB. Measure the resistance
between the NA8- ⑧
chassis ground screw.
Is the resistance <1 ?
Put a jumper between NA8- ⑥ (YL)
and NA8- ⑦ (BL) to create a circuit
connection for the continuity test in
the next step.
Measure the resistance between
the two moisture
sensor bars on the in the lint filter
housing inside
the drum. Is the resistance <1
Check all connections and wires
between the NA8
terminal at the main PCB and the
sensor bars.
Check the resistance is 0
• Measure the resistance of all wires.
Resistance should be <1
• Check all sensor harness connectorsfor corrosion,
loose/bent pins, broken wires, etc.
• Check all harness wires between the main PCB and the
sensor for cuts, or broken wires.
NO
(GN) pin and a
YES
YES
YES
?
NO
YES
?
36
• Check all wiring
harness connections
wire and Ground
screws.
• Replace the main
PCB.