the turntable in my lg microwave just spins sometimes and other times it doesn't move at all.

Diagnosis

The intermittent rotation of the turntable in the LG LMV2031ST is typically caused by a mechanical failure in the drive coupling system or a failing synchronous motor. When the turntable spins occasionally but stalls during other cycles, it indicates that the motor is still receiving power, but the physical transfer of torque from the motor shaft to the glass tray is being interrupted. This is often due to a "stripped" drive hub—the plastic piece that sits between the motor and the roller ring—where the square socket has worn down into a circle, allowing the motor shaft to spin freely without gripping the hub. Another common cause is debris accumulation or "sugar-glaze" buildup under the roller ring. If food spills have seeped under the plastic ring, they create a sticky residue that increases the friction load on the motor. Because the turntable motor is a low-torque synchronous motor, even a small amount of resistance can cause it to stall. You can confirm this by removing the glass tray and observing the drive hub; if the hub spins but the tray doesn't, the hub is stripped. If the hub doesn't spin at all while the microwave is running, the motor is likely failing or the drive coupling is disconnected.

How to Fix It

To resolve this issue, you must first determine if the failure is the plastic hub or the motor itself. Follow these steps for a full mechanical restoration:

1. Power down the unit completely by unplugging it from the wall outlet or flipping the circuit breaker to ensure safety.
2. Remove the glass turntable tray and the plastic roller ring (the wheel assembly).
3. Locate the drive hub (the plastic coupling) in the center of the microwave floor. Inspect the square hole where the motor shaft inserts. If the hole looks rounded or there are visible cracks in the plastic, the hub is stripped.
4. Remove the faulty hub. If it is stuck, use a flat-head screwdriver to gently pry it upward from the edges.
5. Install a new drive hub (Part Number: 6323ER2002A). Press it firmly down onto the motor shaft until it seats completely flush against the cavity floor.
6. Clean the floor of the microwave cavity with a damp cloth and mild detergent to remove any grease or food particles that could cause drag.
7. Reinstall the roller ring, ensuring the wheels are seated correctly in the track, and place the glass tray back on top, aligning the notch of the tray with the tab on the drive hub.
8. Plug the unit back in and test with a microwave-safe bowl of water to ensure consistent rotation.

If That Didn't Work

• Replace the Turntable Motor: If the drive hub is intact but the motor shaft does not rotate, the synchronous motor has failed. You will need to remove the outer chassis of the microwave to access the motor mounted underneath the cavity floor. Disconnect the two wire leads, unscrew the motor mounting bracket, and install a new motor assembly. Ensure the shaft is perfectly vertical before tightening the screws.
• Check the Roller Ring Wheels: Inspect the wheels on the bottom of the plastic roller ring. If one of the wheels is flat-spotted or seized due to melted plastic or debris, it creates an uneven load that can stall the motor. Replace the entire roller ring assembly if any wheel does not spin freely by hand.
• Inspect the Glass Tray Base: Examine the underside of the glass turntable. If the center recessed area is chipped or worn, it may not be seating properly on the drive hub, causing it to slip. If the glass is uneven, it will cause the motor to struggle and eventually stop.
• Test for Voltage: Using a multimeter, check for 120V AC at the motor terminals while the unit is running. If there is no power reaching the motor, the issue is likely a failed relay on the main control board rather than a mechanical failure.

Heads Up

• High Voltage Warning: Never open the outer casing of the microwave unless you are trained in discharging the high-voltage capacitor. The capacitor can hold a lethal charge even when the unit is unplugged.
• Avoid Overloading: Do not place excessively heavy containers (over 10 lbs) on the turntable, as this puts undue stress on the plastic drive hub and will cause it to strip prematurely.
• Regular Cleaning: Wipe down the area under the roller ring once a month. Dried food spills act like glue and are the leading cause of motor burnout in over-the-range models.
• Alignment Check: Always ensure the glass tray "clicks" into the hub. If the tray is slightly off-center, it will wobble, creating a centrifugal force that can snap the drive hub during operation.