LG Dishwasher Sensor Replacement — Thermistors, Turbidity, and Water Level

LG dishwashers use multiple sensors to monitor water temperature, water level, soil level, and door position. When people say their LG dishwasher needs a sensor replaced, they usually mean one of three components — and each is a completely different part, in a different location, with different symptoms and testing procedures.

The Three Main Sensors in LG Dishwashers

Thermistor (temperature sensor): An NTC (negative temperature coefficient) resistor that measures water temperature. Located near the flow-through heater assembly below the tub. When it fails, the dishwasher cannot regulate wash temperature — you get HE errors, lukewarm water, or endless cycles as the board waits for a temperature threshold that the broken sensor cannot report.

Turbidity sensor (soil sensor): A light-transmission sensor in the sump that measures how dirty the recirculating water is. The board uses this reading to extend or shorten cycles and adjust water temperature. When it fails, the dishwasher may run excessively long cycles (sensor reads permanently dirty) or excessively short cycles (sensor reads permanently clean).

Water level sensor (pressure switch): Measures the water level in the tub via air pressure in a connected tube. When it fails, the dishwasher may overfill (IE error from the board detecting unexpected water) or underfill (not enough water for effective washing).

Identifying Which Sensor Failed

Part Numbers and Pricing

All three sensors are inexpensive parts. The diagnostic time is worth more than the parts themselves.

Testing Each Sensor

Thermistor: Disconnect the 2-pin connector. Measure resistance with a multimeter. At room temperature (72F), expect approximately 50K ohms. At 150F (measured after a hot cycle), expect approximately 5K ohms. If the reading is infinite (open) or zero (shorted), replace it.

Turbidity sensor: This is harder to test with a multimeter because it is an optical sensor. The easiest test is to clean the sensor window with a soft cloth and clear water. If the symptom resolves, the sensor was just dirty. If it persists, replace the sensor.

Water level sensor: Disconnect the air tube from the sensor and blow gently into the sensor port. You should hear the switch click. If it does not click, the diaphragm inside the sensor is stuck or torn.

Tools Required

• Phillips #2 — for access panels
• Multimeter — essential for thermistor testing
• Small flathead screwdriver — for prying connector tabs
• Flashlight — sensors are in tight spaces beneath the tub

Replacement Procedure by Sensor

Thermistor: Disconnect power. Remove the bottom kick plate. The thermistor is mounted near the flow-through heater with a clip or single screw. Unplug the 2-pin connector, remove the clip, pull the old sensor out, push the new one in. Two-minute swap.

Turbidity sensor: Disconnect power. Remove the bottom panel. The sensor mounts in the sump housing, typically with a twist-lock or single screw. Unplug the connector, remove the sensor, install the new one. Clean the sump area while you have access.

Water level sensor: Disconnect power. Remove the bottom panel. The sensor is typically mounted on the side of the tub near the bottom. Disconnect the air tube and electrical connector. One or two screws hold it in place.

Sensor Lifespan

Thermistors typically last 10-15 years. Turbidity sensors can last the life of the machine if kept clean but may need replacement after 8-10 years if the optical window becomes permanently clouded by mineral deposits. Water level sensors have a rubber diaphragm that degrades over 10-12 years.

Frequently Asked Questions

My LG dishwasher cycles take over 3 hours. Which sensor is bad?

Most likely the turbidity sensor. When stuck reading dirty water, the control board extends the cycle indefinitely waiting for the water to read clean. Clean the sensor first — if the problem persists, replace it ($15-$40).

Can a bad sensor damage other components in my LG dishwasher?

A failed water level sensor can cause overfilling, which may damage the control board if water reaches electrical components. A failed thermistor can cause the heater to run too long if the board has no upper safety limit, though most LG boards have a thermal cutoff as backup.

Are LG dishwasher sensors covered under warranty?

Sensors are covered under the standard 1-year parts and labor warranty. They are not covered by the 10-year motor/compressor warranty.

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