LG Dryer Moisture Sensor & Thermistor Replacement

Which Part, Which Symptom#

Both parts are inexpensive, so the diagnostic time is usually worth more than the components. Exact pricing varies by model.

Two Sensors, Two Jobs#

The moisture-sensor bars are two parallel metal strips mounted inside the drum near the lint-filter opening, about 4-6 inches long. As damp laundry tumbles across them, it bridges a low-voltage circuit; the wetter the load, the lower the resistance, and the board watches that value climb to decide when the load is dry.

The exhaust thermistor is a separate NTC temperature sensor in the outgoing air path. It reads how hot and dry the exhaust is, giving the board a second, independent drying signal that backs up the bars. One measures the clothes directly; the other measures the air they leave behind.

The Dryer-Sheet Film Problem#

The single most common cause of early auto-dry shutoff is not a broken sensor at all — it is a waxy dryer-sheet film on the bars. That invisible coating insulates the metal from wet fabric, so the board reads the load as drier than it is and ends the cycle early. Wipe the bars with rubbing alcohol and a soft cloth once a month; this free step resolves about 70% of auto-dry complaints.

Testing the Exhaust Thermistor#

Unplug the dryer and reach the thermistor from the rear panel or the lint-duct area — it is a small part with a 2-wire connector. Disconnect it and measure resistance: at room temperature expect roughly 10K-50K ohms, and once the air reaches about 150F that should fall to 1K-5K ohms. An infinite reading means it is open, and zero means it is shorted; either way, replace it with 6931EL3003D.

Testing the Sensor Bars#

With the dryer off, meter across the two bar terminals at the control-board connector. Clean, dry bars read open (infinite). Lay a damp cloth across both bars and the resistance should collapse to a few thousand ohms. If nothing changes when the bars get wet, the bars or their wiring have failed.

Replacement Effort#

The thermistor is the quick job — reach it at the rear, unplug the connector, release the clip or screw, and drop in the new one in about ten minutes. The sensor bars are more involved because they mount through the front bulkhead inside the drum; that usually means pulling the front panel and sometimes the drum, closer to an hour of work.

Rule Out a Blocked Vent First#

Before you condemn either sensor, confirm the exhaust vent is clear. A lint-packed vent traps hot, humid air in the drum, which fools even a healthy thermistor into ending the cycle late and leaves clothes damp on auto-dry — the same symptom as a coated sensor bar. Disconnect the vent at the wall, run a short cycle, and see whether drying suddenly improves. If it does, the vent, not the sensor, was the problem, and no part swap is needed.

Keep the two failures straight: a coated bar ends the cycle early, while a blocked vent or a failing thermistor tends to run it long. Testing the resistance settles which one you actually have.

Warranty and Tools#

You only need a multimeter, a Phillips #2 screwdriver, and rubbing alcohol for the whole job. LG covers the sensors under the standard 1-year parts warranty; note they are not part of the 10-year Direct Drive motor warranty, which covers the motor only.