LG Dryer HS: The Moisture Sensor Cannot Read Your Clothes

HS means the humidity/moisture sensor bars inside the drum are not providing a valid signal to the control board. These sensors measure how much moisture remains in your clothes during auto-dry cycles. When they fail, the dryer cannot determine when clothes are dry and either runs indefinitely or shuts off too early.

How the Moisture Sensor Works

Inside the LG dryer drum, near the lint screen opening, you will find two parallel metal bars (typically stainless steel or nickel-plated) approximately 4-6 inches long. These are the moisture sensor bars.

The board sends a small electrical current through one bar, through the tumbling clothes that contact both bars simultaneously, and back through the other bar. Wet fabric conducts electricity. Dry fabric does not. The board measures the resistance of this fabric-bridge between the two bars. As clothes dry, resistance increases. When resistance exceeds the threshold for the selected dryness level (Normal, More Dry, Less Dry), the cycle ends.

HS triggers when the board detects one of these conditions:

• Zero conductivity between bars continuously (even with wet clothes) — bars are coated or disconnected
• Erratic signal that does not follow a drying curve — bar connection is intermittent
• Resistance value outside the measurable range — sensor circuit open or shorted

The Most Common Cause: Dryer Sheet Residue (60%)

Dryer sheets deposit a thin waxy film on the sensor bars. This film is an electrical insulator — it prevents wet fabric from making conductive contact with the metal surface. After months of dryer sheet use, the coating builds thick enough that even soaking wet clothes register as "dry" to the board.

Before dryer sheet buildup triggers a formal HS code, you will notice symptoms:

• Auto-dry cycles ending with damp clothes
• Timed cycles working normally but auto-dry cycles running only 15-20 minutes
• The More Dry setting still leaves clothes damp

Cleaning the sensor bars:

1. Locate the two metal bars inside the drum near the lint screen housing
2. Dampen a cloth with rubbing alcohol (isopropyl 70% or higher)
3. Scrub each bar firmly along its entire length. The waxy buildup is invisible but you can feel it — the bar surface goes from slightly slick (coated) to grippy (clean)
4. Repeat until a clean white cloth rubbed across the bar picks up no residue
5. Run a test auto-dry cycle with damp towels — the cycle should run significantly longer than before if the bars were coated

This cleaning is a $0 fix and resolves the majority of HS cases. Do it quarterly if you use dryer sheets. Or switch to wool dryer balls, which leave no residue on sensor bars.

Sensor Bar Wiring Failure (25%)

Each sensor bar connects to the main board via a wire that passes through the rear drum bulkhead. The connection point at the bar end is a push-on spade terminal. Vibration from years of tumbling can loosen these terminals or break the wire at the crimp point.

Testing:

1. Unplug the dryer
2. Access the sensor bar connections (usually requires removing the dryer's front panel or drum)
3. Measure continuity from each bar to its corresponding board connector terminal
4. A loose spade terminal is visible — push it firmly back onto the bar tab. If the terminal is rounded or cracked, crimp a new spade terminal onto the wire

Sensor Bar Physical Damage (10%)

Heavy items (belt buckles, zippers, shoe snaps) tumbling against the sensor bars can bend, scratch deeply, or physically break a bar. A bent bar that no longer contacts tumbling clothes cannot form the conductive path. A deeply scratched bar may have damaged the plating enough to corrode.

Inspect both bars visually. They should be straight, parallel, and free of deep gouges. Replacement bars (model-specific, $15-30) mount with two screws and have push-on terminals.

Board Sensor Input (5%)

The board's moisture sensor circuit has failed. The bars are clean, wired properly, and physically intact, but the board cannot process the signal. This is rare and usually accompanied by other board symptoms.

Parts and Cost

HS and Auto-Dry vs. Timed Dry

HS only affects auto-dry cycles. Timed cycles ignore the sensor bars entirely — the dryer runs for the time you selected regardless of moisture level. If HS appears and you need to use the dryer immediately, switch to a timed cycle. Set 40-50 minutes for a normal load. This bypasses the sensor entirely but requires you to check clothes manually for dryness.

Fabric Softener in Wash vs. Dryer Sheets

Liquid fabric softener added during the wash cycle does not coat the dryer sensor bars because it bonds to the fabric during the rinse cycle. Dryer sheets work by transferring a waxy coating from the sheet to the fabric during tumbling — and this same coating also transfers to every surface the fabric touches, including the sensor bars. If HS is a recurring problem, switching from dryer sheets to liquid softener eliminates the sensor coating issue entirely.

Small Loads and HS False Triggers

Very small loads (a single towel, a few items) may not maintain continuous contact with both sensor bars as they tumble. The board reads erratic signals — sometimes conductive, sometimes not — which can trigger HS on some LG models. This is a false trigger, not a sensor failure. Run a normal-sized load to verify. If HS clears with a full load, the sensor is fine — small loads simply do not provide enough fabric contact for reliable readings.

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LG dryer ending cycles with damp clothes? Sensor bar cleaning takes 2 minutes and fixes 60% of HS cases — we handle the rest same-visit. Book sensor diagnosis.