LG Dishwasher Thermostat Replacement — The Safety Cutoff You Might Not Know Exists

The thermostat in an LG dishwasher is not the same component as the thermistor. This distinction is critical because replacing the wrong one wastes money and leaves the actual problem unsolved. The thermistor is a temperature sensor that reports water temperature to the control board. The thermostat is a bi-metal safety cutoff that physically disconnects power to the heating circuit if the water exceeds a safe maximum temperature.

Thermostat vs Thermistor — Understanding the Difference

Thermostat (hi-limit cutoff): A bi-metallic disc that physically opens a circuit when temperature exceeds a preset threshold (typically 190-210F). It is a safety device that prevents the heating element from overheating the water to dangerous levels. Some are resettable (push the reset button), others are one-shot (they open permanently and must be replaced).

Thermistor (temperature sensor): An NTC resistor that varies its electrical resistance based on temperature, sending a continuous analog signal to the control board. Covered in the sensor replacement guide.

If your dishwasher has an HE error and the water is cold, the thermistor is more likely the culprit. If the dishwasher was working fine and then suddenly stopped heating with no error code, the hi-limit thermostat may have tripped.

How the Hi-Limit Thermostat Works

The thermostat sits in series with the heating element circuit. Under normal operation, it is closed (conducting) and the heater operates normally under control board regulation. If the thermistor fails and the board keeps the heater on indefinitely, the water temperature rises past the safe limit and the thermostat opens, cutting power to the heater.

This is a last-resort safety mechanism. If the thermostat has tripped, something else caused the overheating — usually a failed thermistor, a stuck relay on the control board, or a wiring issue. Replacing the thermostat without finding the root cause means it will trip again.

Symptoms of Thermostat Failure

• No heat during any cycle, but no HE error code — the thermostat has opened and the heater has no power, but the board may not detect this condition on all models
• Previously tripped and reset but now will not reset — the bi-metal disc has weakened from repeated trips
• Dishwasher stopped heating suddenly after a period of normal operation — the thermostat tripped due to an upstream overheating event

Part Numbers and Pricing

Testing the Thermostat

Disconnect power. Access the thermostat from below by removing the kick plate. The thermostat is typically mounted near the heating element or on the sump housing. Disconnect the two wires.

Set your multimeter to continuity. Touch the probes to the thermostat terminals. At room temperature, you should have continuity (the thermostat is closed). If you get no continuity (open), the thermostat has tripped. Check for a reset button on the back — press it and retest. If it resets and you get continuity, the thermostat tripped but is still functional. If it will not reset, replace it.

Tools Required

• Multimeter — the only way to confirm thermostat status
• Phillips #2 — for kick plate and mounting screws
• Small flathead — for wire connector tabs

Replacement Procedure

The thermostat typically mounts with a single screw or spring clip near the heater assembly. Disconnect the two wires, remove the mounting hardware, and install the new thermostat. Reconnect the wires (not polarized — either terminal works). Before restoring power, investigate why the thermostat tripped. Test the thermistor resistance and inspect the control board for signs of relay damage.

Finding the Root Cause

A tripped thermostat is a symptom, not a cause. Before restoring the dishwasher to service:

1. Test the thermistor — if it reads open or shorted, it likely caused unregulated heater operation
2. Inspect the control board — look for a scorched or pitted heater relay
3. Check wiring — a loose connection on the heater circuit can cause arcing and intermittent overheating

Replacing the thermostat without addressing the root cause is like replacing a blown fuse without finding the short.

Frequently Asked Questions

My LG dishwasher stopped heating but there is no error code. What happened?

The hi-limit thermostat may have tripped, cutting power to the heater. The control board may not detect this condition because it only monitors the thermistor, not the thermostat state. Test the thermostat for continuity.

Can I bypass the thermostat to test if the heater works?

Never bypass a safety thermostat. It exists to prevent water from reaching dangerous temperatures. If the thermostat has tripped, find out why before restoring heater operation.

How often do LG dishwasher thermostats fail?

Rarely on their own. The thermostat is a simple bi-metal device with no moving parts. When it trips or fails, another component (thermistor, board relay) is almost always the underlying cause.

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