LG Dishwasher HE: The Water Is Not Getting Hot Enough

HE means the water temperature inside the tub failed to reach the target temperature within the time limit programmed for the current wash phase. The board commands the heater element on, monitors the NTC thermistor for a temperature rise, and triggers HE when temperature does not increase at the expected rate or stalls below the target.

What the Board Actually Measures

LG dishwashers use an NTC (Negative Temperature Coefficient) thermistor submerged in the sump water. As water temperature increases, the thermistor's resistance decreases. The board reads this resistance through an ADC and converts it to a temperature value.

The HE detection logic is not a simple threshold. The board expects a specific heating curve — approximately 2-3 degrees Fahrenheit per minute when the heater is energized. If the temperature rise rate falls below this curve for longer than the fault timeout (typically 10-15 minutes of stalled temperature), HE triggers. This means the water could be warm (say 100 degrees F) but not rising, and HE still appears.

Three Possible Failure Points

The Heater Element Itself (45%)

The heating element is a tubular metal resistance wire (calrod) mounted in the sump floor, submerged in wash water. Over time, the resistance wire can burn open (creating an open circuit) or the outer sheath can crack and allow water intrusion into the insulation (creating a ground fault).

Testing the element:

1. Breaker off. Access from below through the kick plate
2. Disconnect the two heater wire leads at their connectors
3. Measure resistance across the two heater terminals: expect 10-16 ohms. Infinite (open) = burned out. Near zero = shorted
4. Measure from either terminal to the metal tub/chassis ground: should be infinite. Any reading indicates a ground fault — the element must be replaced even if the resistance test passed

A ground-faulted element may trip the kitchen GFCI or breaker intermittently. If your dishwasher has been tripping its circuit protection, check the heater ground fault measurement before investigating the electrical panel.

The NTC Thermistor (35%)

The thermistor is a small bead or capsule sensor mounted in the sump area, in contact with wash water. It tells the board the current water temperature. If the thermistor has drifted out of specification (reading colder than actual water temperature), the board believes the heater is not working even though it is heating the water normally.

Testing the thermistor:

1. Disconnect the thermistor leads
2. Measure resistance at room temperature (approximately 68 degrees F): expect 5,000-6,000 ohms for most LG dishwasher NTC sensors
3. Hold the sensor body in your closed fist for 30 seconds (warming it to body temperature, approximately 95 degrees F): resistance should drop to approximately 3,000-4,000 ohms
4. If resistance does not change with temperature, or reads infinite/zero, the thermistor is defective

A thermistor that reads 20% higher resistance than specification at room temperature will consistently report water temperature 15-20 degrees lower than actual. The heater works perfectly but the board never sees the target temperature reached — producing chronic HE codes.

Board Heater Relay (20%)

The main board controls the heating element through a relay. If the relay contacts have burned open (or the solder joint cracked from thermal cycling), the board commands heating but no power reaches the element.

Testing the relay output:

1. Reconnect the heater leads
2. Restore power. Start a cycle that includes heated wash
3. Using a non-contact voltage tester near the heater leads during the wash phase — you should detect voltage when the board commands heating
4. If the element tests good (proper resistance, no ground fault) but receives no voltage during the heat phase, the board relay has failed

Element Replacement

The heating element mounts through the sump floor with a compression fitting or nut from below:

1. Breaker off. Pull the dishwasher forward for bottom access
2. Disconnect heater leads and the grounding wire
3. From below, loosen the large nut on the heater mounting bracket (this nut compresses a rubber gasket around the element where it passes through the sump floor)
4. Push the element up through the sump floor from below. Old gasket material may resist — do not force hard enough to crack the sump plastic
5. Clean the mounting hole. Install the new element with the new gasket provided
6. Hand-tighten the mounting nut, then 1/4 turn with a wrench. Over-tightening splits the sump
7. Reconnect wiring and test

Parts and Cost

Why HE Matters Beyond Clean Dishes

The heater serves two critical functions beyond cleaning performance. First, it sanitizes — LG's Sanitize cycle raises water to 150 degrees F to kill bacteria, meeting NSF/ANSI Standard 184. Without the heater, sanitization claims are invalid. Second, the heated dry phase evaporates residual water from dishes. Without heating, dishes come out wet and spotted, and standing moisture in the tub promotes mold growth in the door seal area.

HE on TrueSteam Models

LG TrueSteam dishwashers have a secondary steam generator separate from the main wash heater. This generator boils a small water charge to produce steam for pre-soaking and rinsing. HE can trigger from either the main heater or the steam generator — they are independent circuits monitored separately. If HE appears only during steam-enabled cycles but not during standard wash, the steam generator element is the failure point, not the main heater.

The steam generator is mounted on the upper tub wall behind the spray arm and has its own pair of leads and its own thermistor. Accessing it requires removing the inner door panel and the upper spray arm assembly.

Incoming Water Temperature

LG dishwashers expect incoming hot water at 120 degrees F minimum. If your water heater is set below 120 or the dishwasher is far from the water heater (long pipe run), the incoming water may be lukewarm. The heater then must raise temperature by 40+ degrees instead of 15-20 degrees, sometimes exceeding the fault timeout before reaching target.

Fix: run the kitchen faucet on hot until the water is fully hot before starting the dishwasher. This flushes cool water from the pipe run so the first fill reaches the tub already at temperature.

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LG dishwasher not heating? We test the element, thermistor, and board relay on-site before recommending any parts — no guesswork on a three-variable problem. Book heater diagnosis.