Kenmore Dishwasher Temperature Not Right — Thermistor and Heater Diagnosis

Incorrect water temperature in your Kenmore dishwasher affects cleaning performance, sanitization capability, and drying effectiveness. Temperature complaints fall into two categories: water too cold (most common, covered in detail in the "not heating" guide) and water too hot (less common but potentially damaging to delicate items). The temperature control system architecture differs substantially between Kenmore's OEM platforms, affecting diagnosis approach.

Temperature Control Architecture by Platform

Whirlpool 665 Platform

Whirlpool-manufactured Kenmore dishwashers regulate temperature through a feedback loop:

• Thermistor (NTC sensor) reads water temperature and reports to the control board
• Exposed calrod element heats water when the board determines temperature is below target
• Target temperatures: Normal wash 130F, Heavy/Pots 140F, Sanitize 150F, Rinse 155F
• Turbidity sensor also influences cycle length — clear water may end a phase even if temperature has not reached maximum

The control board cycles the heater on and off in response to thermistor readings. If the thermistor fails, the board cannot regulate temperature and may default to either continuous heating (overheating risk) or no heating (under-heating).

LG 630 Platform

LG-manufactured Kenmore dishwashers use a slightly different approach:

• Thermistor integrated into the sump housing
• Concealed heater beneath the sump (not visible in tub)
• Target temperatures: Similar ranges but LG platform heats the final rinse hotter (170F) for condensation drying effectiveness
• Temperature gate: The board will NOT advance between certain phases until water reaches a minimum temperature threshold

The LG platform is more aggressive about temperature compliance — if the heater cannot reach target within a timeout period, it displays error HE or tE rather than proceeding with cold water.

Water Too Cold

Most Common Cause: Low Incoming Water Temperature

Before diagnosing internal components, verify your hot water supply. The dishwasher's heater is designed as a BOOST system — it expects incoming water at 110-120F and boosts it the remaining 10-30 degrees. If your water heater is set below 120F, or if the dishwasher is far from the water heater (long pipe run), incoming water may be 80-90F — too low for the dishwasher's heater to compensate within its timeout period.

Quick test: Run the kitchen hot water tap for 2 minutes to prime the line. Immediately start the dishwasher. If cleaning performance improves dramatically, the issue is cold incoming water rather than a dishwasher component failure.

Thermistor Drift or Failure

A thermistor that drifts out of calibration provides incorrect readings to the control board:

• Reading too high: Board thinks water is hotter than actual — cuts heater power prematurely. Result: water never reaches target temperature.
• Reading too low: Board thinks water is colder than actual — runs heater past target. Result: water overheats.
• Open circuit: Board receives no reading — behavior varies by platform (665 may default to no heat as safety measure; 630 displays error tE).

Testing the thermistor:

1. Disconnect power and access the thermistor connector.
2. Measure resistance with a multimeter at room temperature (72F):
   • Whirlpool 665: approximately 55k ohms
   • LG 630: approximately 50k ohms
3. The reading should decrease as temperature increases. Place your hand around the sensor and watch the resistance drop — confirms the sensor responds to temperature change.
4. A reading of infinite ohms = open (broken). A reading of zero ohms = shorted.

DIY Difficulty: Moderate Parts Cost: $15–$40 for thermistor Professional Repair Cost: $120–$200

Water Too Hot

Thermistor Reading Low (All Platforms)

If the thermistor tells the board that water is 90F when it is actually 150F, the board continues heating well past the target. On Whirlpool-platform 665 models, this can produce steam from the vent and extremely hot dishes that are dangerous to handle immediately after the cycle. On LG-platform 630 models, the concealed heater has a secondary thermal cutoff that will trip before the water reaches a dangerous level.

Control Board Relay Stuck On (Whirlpool 665 Platform)

If the heater relay on the control board welds shut (contacts fused together from a power surge or age), the heating element receives continuous power regardless of thermistor feedback. The element never shuts off during the cycle. This condition will eventually trigger the thermal fuse as a safety measure, but before that happens, water can reach scalding temperatures.

Diagnosis: If water seems excessively hot AND the heater is still running when you open the door during a rinse phase (element visibly glowing on 665 models), the control board relay is stuck. Replace the control board.

DIY Difficulty: Moderate Parts Cost: $95–$250 for control board Professional Repair Cost: $220–$400

High Incoming Water Temperature

If your water heater is set to 140F or higher, and the dishwasher further boosts this temperature, the result can be water approaching 170-180F — well above what is needed for normal wash and potentially damaging to certain plastics and delicate items.

Fix: Set your home water heater to 120F (also prevents scalding at sinks and showers). The dishwasher's internal heater is designed to make up the difference.

Sanitize Cycle Temperature Requirements

The NSF-certified sanitize cycle on Kenmore dishwashers (available on both Whirlpool and LG platforms) must reach and hold water at 150F minimum for a specified duration. If your Kenmore cannot achieve this temperature:

• The sanitize indicator light will blink or not illuminate at cycle end (Whirlpool 665)
• An error displays on the panel (LG 630)
• The cycle extends trying to reach temperature, then eventually completes without sanitization

This is usually the first symptom noticed when a heater begins to fail — sanitize stops working weeks before normal cleaning performance degrades noticeably.

Temperature Calibration (Not Available on Most Platforms)

Unlike ovens, most Kenmore dishwasher platforms do not allow user-adjustable temperature calibration. The thermistor reading is accepted at face value by the control board. If you suspect temperature inaccuracy but the thermistor tests within specification, the only verification is placing a waterproof thermometer in the tub during a cycle and comparing the actual temperature to the expected target for your selected cycle.

Kettle Test for Temperature Verification

A practical way to verify your Kenmore is reaching proper wash temperature without a waterproof thermometer:

1. Run a full Normal cycle with no dishes except a ceramic mug placed upside-down on the top rack.
2. Open the door immediately when the wash phase ends (before drain — timing varies by model).
3. Carefully touch the ceramic mug. At 130F (correct Normal temperature), the mug will be too hot to hold comfortably but will not burn instantly.
4. If the mug is merely warm (100-110F), the heater is underperforming.
5. If the mug is scalding hot (uncomfortable to even briefly touch), the temperature is excessive.

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Kenmore dishwasher temperature issues? Our technicians measure actual water temperature with calibrated probes and test thermistor accuracy on-site for both Whirlpool and LG platform units. Schedule a repair →