Unplug your Whirlpool Duet washer from the wall receptacle.
Remove the three screws along the bottom front of the washer. Pull the bottom panel from the washer, opening the front of the washer.
Reach your arm up through the opening to locate the door latch assemble inside the body of the washer. Grasp the tear-shaped tab with your fingers. Gently pull down on the tab until you hear a click. Pull on the Duet door to open it.
Look inside the latch opening in the body of the washer for foreign material. Remove it from the switch with tweezers or needle-nose pliers. Look for any pieces of broken plastic that could indicate the door lock mechanism is broken and needs replacing.
Shut the door on the washer and plug it into the wall receptacle. Confirm that the door remains unlocked. Unplug the washer and release the lock on the washer door as before if it fails to remain unlocked.
Unplug the Duet washer from the receptacle. Pull the washer from the wall so you can access the rear of the washer.
Remove the three screws from the top back of the Duet washer. Lift the top off the washer. Find the central control unit, or CCU, at the back right of the washing machine.
Check that all the wiring harnesses plug securely into the CCU. The wiring harness for the door-lock solenoids is the sixth harness from the left of the CCU. The wiring harness for the door-lock main switches is the only black harness connected to the CCU.
Remove the round retainer holding the rubber boot gasket from the Duet washer door opening by inserting a flat-head screwdriver beneath the spring on the retainer. Pull forward on the retainer spring to release it from the boot gasket.
Pull the rubber boot gasket away from the opening at the switch location to access the door switch assembly. Check the wiring harness on the switch assembly to make sure it is engaged. Snap the gasket back in place, and replace the retainer on the washer.
Plug the Duet washer into the wall receptacle. Select a washing cycle and press start. Listen for the door lock to engage. Turn the washer off and listen for the door lock to disengage, or wait 30 seconds and try to open the washer door.
Unplug the washer from the wall receptacle. Pull the wiring harness for the door-lock solenoids from the CCU. Number the sets of wires attached to the wiring harness as 3, 2 and 1, from left to right.
Set an electrical multimeter to "Ohm X1K." Insert one probe from the multimeter into opening number 3, along with the wire. Insert the remaining probe into opening number 2, along with the wires. The multimeter should read 60 ohms. Leave the probe in opening number 3, and move the remaining probe to opening number 1. The multimeter should read 60 ohms in this position as well. Should you receive any other reading, replace the wiring harness.
Reconnect the wiring harness for the door-lock solenoids into the CCU. Plug the Duet washing machine into the wall receptacle. Select a wash cycle on the duet, then press start. Listen for the door lock to engage and immediately unplug the washer from the wall.
Leave the wiring harness for the door-lock main switches plugged into the CCU. Number the wires in the harness 5, 4, 2 and 1, from left to right. The middle opening on the wiring harness is empty, so there isn't a third wire.
Set the dial on the electrical multimeter to "Ohms X1K." Insert one probe into the opening next to wire 5, and insert the remaining probe into the opening next to wire 4. The meter should read zero ohms.
Insert one probe into the opening next to wire number 2, and insert the remaining probe into the opening next to wire 1. The meter should read zero ohms. Replace the wiring harness should you receive any other reading.
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