LG WM3700HWA — 03 Door Lock Error: What Causes It and How to Fix It
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Understanding the Problem
Brief explanation: Many LG front-load washers (including the WM3700HWA) show an error related to the door locking system when the washer thinks the door did not lock or unlock properly. This can appear as an "03" or a door lock-related code and causes the washer to stop, refuse to start, or not drain or spin. The most common causes are a failed door lock (latch) assembly, a damaged door strike/catch, wiring or connector issues, or a control board fault. Step-by-step diagnostic and repair steps: 1) Confirm the symptom and reset power - Note the exact error display and behavior (won't start, won't unlock, stuck mid-cycle). Power-cycle the washer by unplugging it or switching off the breaker for 1–2 minutes, then restore power. If the code clears but returns, continue diagnostics. 2) Observe and listen during a door-lock attempt - Start a quick cycle and listen at the door area. A working lock will often make a distinct click as it energizes. If you hear nothing, the lock may not be getting power or is failed. 3) Check the door latch & strike physically - Inspect the door strike on the door and the lock assembly on the frame for cracks, broken plastic, or worn parts that prevent engagement. Damaged strike pieces can prevent the lock from sensing a closed door. 4) Inspect the wiring and connector - Unplug the washer. Open the top/front access panel to locate the door lock harness (usually routed to the front top corner). Check the harness and connector for pins pushed out, corrosion, burn marks, or loose connections. Wiggle-test wiring for intermittent faults. 5) Test the door lock assembly (electrical check) - With the washer unplugged, disconnect the door lock harness and check the lock for continuity with a multimeter (ohms). A completely open circuit usually indicates a failed lock. If you know the expected resistance from the service manual, compare to spec. If you can safely power the washer and have experience, you can measure the voltage at the harness while commanding a lock (careful—live voltage present). If the control board is sending voltage but the lock doesn't actuate, the lock is faulty. 6) Bypass test only for experienced users/technicians - Some techs temporarily short the lock signal to trick the machine into thinking the door is locked for testing purposes. This is for diagnostic use only and not a permanent fix. Do not run the washer with the door physically prevented from locking. 7) Replace the door lock/latch assembly if failed - If the lock shows no continuity or doesn't activate when voltage is present, replace it. Confirm you buy the correct OEM part for WM3700HWA (see parts list below). Replacement typically requires removing the front/top panel or opening the door boot to access the lock—steps provided below. 8) Reassemble and test - After replacing the lock and reconnecting all wiring, restore power and run a test cycle to confirm the error is gone and the door locks/unlocks correctly. Basic replacement procedure (how to fix) — typical front-load LG washer door lock replacement: 1. Unplug the washer and shut off water. Ensure the washer is empty. 2. Open the washer door and remove the retaining screws visible around the inner door frame or on the front panel that secure the latch (some models require removing the top panel first). Keep track of screws. 3. Pull the latch/lock assembly forward enough to access the wire connector behind it. Disconnect the wiring harness (press the tab and pull straight out). 4. Remove the lock assembly screws and take out the old lock/latch. 5. Install the new lock assembly in the exact orientation, secure screws, and reconnect the harness firmly. 6. Reinstall any panels removed, restore power, and run a short cycle to verify operation. Safety note: Always unplug the washer or switch off the circuit breaker before opening panels or handling wiring. If you are not comfortable working with live circuits or opening the cabinet, hire a qualified appliance technician.
Common Symptoms
Error code related to door lock (displayed as "03" or a door icon), washer won't start or proceed past the door-lock stage, door stuck locked or won't unlock, no audible click when cycle starts.
Common Causes
- Failed door lock / latch assembly
- Damaged door strike or misaligned door preventing latch engagement
- Broken or corroded wiring/connector between the lock and main control
- Control board not sending lock signal (less common)
Popular Parts That Fix This Problem
These are the most common replacement parts that fix this problem. When you're ready to order, click below to find the right part at ProsourceParts.com — just search by your appliance model number for a guaranteed fit.
Helpful Repair Tip
Listen for the door-lock 'click' when starting a cycle and check for continuity across the lock terminals with a multimeter; no click plus no continuity almost always means the door lock assembly needs replacing.
Frequently Asked Questions
Can I reset the '03' door lock error myself?
You can try a simple reset by unplugging the washer or switching off the breaker for 1–2 minutes and then restoring power. If the error returns, follow the diagnostic steps above — a reset rarely fixes a failed door lock assembly permanently.
How much does it cost to replace the door lock on an LG WM3700HWA?
Part cost for an OEM door lock assembly typically ranges from $30–$120 depending on vendor and genuine vs. aftermarket. Labor (if done by a technician) usually adds $80–$200. If you do the replacement yourself, budget for the part plus basic tools; it's a moderately easy DIY for someone comfortable with appliance panels and wiring.
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