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Error code reference

Miele Dishwasher Error Code F26

Boiling protection

Miele codesMiele dishwasher codes

Boiling protection — maximum safety temperature of 194°F at NTC sensor exceeded; program interrupted and drain pump operated.

First step from the service manual

Check heating relay to see if it is fused closed; check NTC temperature sensor for accuracy.

The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.

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What F26 means on a Miele dishwasher

The F26 error code on a Miele dishwasher indicates a boiling protection fault. The machine's NTC (negative temperature coefficient) thermistor sensor detected that the wash water temperature exceeded the maximum safety threshold of 194°F. When this threshold is crossed, the control board immediately interrupts the active wash program and activates the drain pump to remove the overheated water from the tub. This is a protective function designed to prevent damage to the dishwasher interior, the dishes, and potentially the user.

The most likely cause of an F26 fault is a heating relay that has fused in the closed position. When a relay contact welds shut, it sends continuous power to the heating element regardless of what the control board commands, causing the water temperature to climb unchecked until the NTC sensor triggers the safety cutoff. A faulty or inaccurate NTC sensor is the other primary suspect, as a sensor that reads lower than the actual water temperature would allow the heater to run longer than it should, or one that misreads in the opposite direction could trigger a false F26 even when actual temperatures are normal.

Diagnosis should begin with inspecting the heating relay on the control board for signs of contact fusion or heat damage. The NTC sensor should then be tested for resistance accuracy across a range of temperatures to confirm it is reporting correctly to the control board. Both components are critical to the thermal regulation system, and a failure in either one can produce this fault.

Source: manufacturer service documentation.

Common causes of F26

  1. 01

    Heating relay fused closed

    Part replacement

    If the relay contacts that control the heating element have welded together, the heater receives continuous power and cannot be shut off by the control board, driving temperatures past the 194°F safety limit. Inspect the relay on the control board for heat discoloration or physical damage, and test for continuity with power removed.

  2. 02

    Faulty NTC temperature sensor

    Part replacement

    An NTC sensor that has drifted out of calibration or failed can report inaccurate temperatures to the control board, either triggering a false F26 or allowing actual overheating to occur before the fault is detected. Test the sensor's resistance value against the expected range at a known water temperature.

  3. 03

    Control board fault

    Part replacement

    If the control board itself is malfunctioning, it may fail to cut power to the heating element at the correct temperature setpoint even when the relay and NTC sensor are functioning properly. This is less common but should be considered after the relay and sensor have been ruled out.

  4. 04

    Wiring or connector issue between NTC and control board

    Wiring / connection

    Loose, corroded, or damaged wiring between the NTC sensor and the control board can cause erratic temperature readings, leading the system to mismanage heating cycles and potentially trigger the F26 safety cutoff. Inspect the wiring harness and connectors for visible damage or poor contact.

See the test procedure for each cause

Frequently asked questions about F26

What does F26 mean on a Miele dishwasher?
F26 is a boiling protection fault indicating the water temperature inside the dishwasher exceeded the maximum safety limit of 194°F as measured by the NTC temperature sensor. When this happens, the dishwasher immediately stops the current wash program and runs the drain pump to remove the overheated water. The fault points to either a heating relay stuck in the closed position or an inaccurate NTC sensor.
Can I fix the F26 error myself?
Some diagnostic steps, such as inspecting wiring connections to the NTC sensor, are accessible to a knowledgeable DIYer. However, testing the heating relay for fused contacts and verifying NTC resistance accuracy require a multimeter and comfort working with appliance electronics. If the relay or sensor needs to be replaced, the repair involves accessing internal components, which many homeowners prefer to leave to a qualified technician.
Is it safe to use my dishwasher while it shows F26?
No, the dishwasher should not be used until the underlying cause of the F26 fault is diagnosed and resolved. The fault exists because water reached a dangerously high temperature, and continuing to run the machine without fixing the root cause, particularly a stuck heating relay, risks damaging the appliance, its internal components, and potentially the surrounding cabinetry.
Will resetting the dishwasher clear the F26 error?
A reset may temporarily clear the fault code display, but it will not fix the underlying problem. If the heating relay is fused closed or the NTC sensor is faulty, the fault will return during the next wash cycle once the temperature again exceeds 194°F. The root cause must be repaired before the machine will operate reliably.
How much does it cost to repair an F26 error on a Miele dishwasher?
Repair costs vary depending on which component has failed. An NTC sensor replacement is typically the less expensive repair, while a control board replacement with a fused relay represents the higher end of the cost range. Including parts and labor, most F26 repairs fall somewhere between $150 and $450, though costs can vary based on your location and the specific parts required.

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