LG Washer Error Code H4

H4 is a thermistor wash overheating error indicating that the wash heater operated without sufficient water in the tub, or that the wash thermistor itself is defective. The washer stops the cycle automatically when this condition is detected to prevent damage to the heating element and other components. Diagnosis starts with confirming that the washer is filling to the correct water level before the heating phase begins.

You should not continue running the washer while H4 is active. The error indicates that the heater may have operated in a dry or low-water condition, which can damage the heating element and potentially affect other internal components. Stop the cycle and diagnose the root cause before using the machine again.

Repair costs depend on which component has failed. A wash thermistor is generally an inexpensive part, with parts and labor typically ranging from around $75 to $175. If the water inlet valve requires replacement, costs are often in the $100 to $200 range including labor. A control board replacement is the most expensive possibility, often ranging from $200 to $400 or more depending on the model and service rates in your area.

Start by checking that both hot and cold water supply valves are fully open and that water pressure is adequate. Inspect the inlet valve screens for debris that could restrict water flow into the tub. If fill looks normal, test the wash thermistor with a multimeter to confirm it is reading resistance within the expected range for the water temperature. If the thermistor is faulty, replacing it should clear the error.

A reset may temporarily clear the H4 code, but if the underlying problem is not fixed, the error will return as soon as the washer reaches the heating phase again. If the cause is a defective thermistor or a water fill issue, those components need to be repaired or replaced for the fix to be permanent.