LG Dishwasher Thermostat Replacement

Keeping those two parts straight is the whole battle. The thermistor is an NTC sensor that reports water temperature to the control board continuously. The hi-limit thermostat is a last-resort safety device that opens the circuit when temperature exceeds a preset threshold, typically somewhere around 190°F to 210°F. Some hi-limits are resettable with a small button; others are one-shot fuses that open permanently and must be replaced. As a rule of thumb, a cold-water HE error points more toward the thermistor, while an oven that was heating fine and then suddenly stopped with no code points toward a tripped hi-limit.

How it works, and how it fails#

The hi-limit sits in series with the heating element and stays closed under normal operation, letting the board regulate the heater. If the thermistor fails and the board keeps the heater on indefinitely, the water climbs past the safe limit and the disc opens, cutting power. So the symptoms are telling:

• No heat on any cycle but no HE code — the disc has opened and the heater has no power, and the board may not flag it
• Previously tripped and reset, now will not reset — the bi-metal has weakened from repeated trips
• Heating stopped abruptly after normal operation — an upstream overheat tripped the disc

Testing and replacing#

Cut power and drop the kickplate to reach the thermostat, mounted near the heating element or on the sump housing, and disconnect its two wires. On continuity, at room temperature it should read closed; an open reading means it tripped. Check for a reset button on the back — if it resets and reads closed, it tripped but still works; if it will not reset, replace it. To swap it, remove the single screw or spring clip, transfer the two (non-polarized) wires to the new disc, and mount it — but do not restore power yet.

Tools are minimal: a multimeter, a Phillips #2 for the kickplate, and a small flat screwdriver for the connector tabs. The related one-shot thermal fuse is a separate part (6931EL3001A) if your model uses one.

Find the root cause before you close it up#

A tripped hi-limit is a symptom, not a diagnosis. Before returning the dishwasher to service, run three checks: test the thermistor, because one reading open or shorted can drive the heater with no regulation; inspect the control board for a scorched or pitted heater relay that could be stuck closed; and check the heater wiring for a loose connection that can arc and overheat intermittently. Replacing the thermostat while ignoring those is like swapping a blown fuse without finding the short — the new disc will trip again on the next cycle. And never bypass a safety thermostat to "test" the heater; it exists specifically to keep water from reaching dangerous temperatures, so if it has tripped, the correct response is to find out why, not to defeat it. Reassuringly, these discs rarely fail on their own — they are simple, moving-part-free devices — so when one trips, the real culprit is almost always the thermistor or a board relay.

Resettable vs. one-shot#

Know which type your dishwasher uses before you shop. A resettable hi-limit has a small button on the back and can be restored once if the trip was a one-time event, but a disc that keeps tripping has weakened and should be replaced rather than reset again and again. A one-shot thermal fuse has no button at all — it opens permanently and is simply swapped. Either way, the disc or fuse only did its job because the water got too hot, so pair any replacement with a thermistor test; a healthy safety part protecting a healthy heating circuit should essentially never trip during normal use.