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Error code reference

Miele Dishwasher Error Code F79

Circulation pump communication fault; faulty communication between the circulation pump frequency converter…

Miele codesMiele dishwasher codes

Circulation pump communication fault; faulty communication between the circulation pump frequency converter electronic and the control-power electronic (SLT).

First step from the service manual

Check for supply voltage at the electronic (SLT) output/input, wiring harness, and circulation pump.

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

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  • Wiring diagram references and connector pinouts from the OEM service manual
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What F79 means on a Miele dishwasher

Error code F79 on a Miele dishwasher indicates a communication fault between the circulation pump's frequency converter electronic and the main control power electronic, known as the SLT. The circulation pump in these machines is driven by a variable-speed motor controlled through a frequency converter, which allows the pump to operate at different speeds depending on the wash program. The SLT acts as the central control board, sending commands to and receiving feedback from the frequency converter. When this communication link breaks down or produces signals outside of acceptable parameters, the machine halts and logs F79.

The fault can originate from several points in the communication chain. A failed or intermittent wiring harness between the SLT and the frequency converter electronic is a frequent contributor, as connectors can corrode, pins can back out, or wires can chafe against cabinet edges over time. Loss of supply voltage at the SLT output or input is another primary suspect, since the frequency converter requires stable voltage to maintain communication with the control board. The fault can also point to a failure within the frequency converter electronic itself or within the circulation pump motor.

Diagnosis begins with verifying supply voltage at the SLT output and input terminals, then inspecting the wiring harness for continuity, damaged insulation, and secure connector seating. If voltage and wiring check out, the frequency converter electronic and the circulation pump itself should be evaluated. Replacing a faulty wiring harness or defective electronic component will typically be required to resolve the fault permanently.

Source: manufacturer service documentation.

Common causes of F79

  1. 01

    Wiring harness fault

    Part replacement

    Damaged, corroded, or loose wiring between the SLT control board and the circulation pump frequency converter is a leading cause. Inspect the harness for broken wires, corroded pins, and connectors that are not fully seated.

  2. 02

    Supply voltage loss at SLT output or input

    Wiring / connection

    If the SLT is not delivering or receiving the correct supply voltage, communication with the frequency converter will fail. Check voltage at both the input and output terminals of the SLT using a multimeter.

  3. 03

    Failed frequency converter electronic

    Part replacement

    The frequency converter module that controls pump speed can fail internally, preventing it from communicating with the SLT. If voltage and wiring are confirmed good, the frequency converter board is the next component to evaluate for replacement.

  4. 04

    Faulty circulation pump motor

    Part replacement

    A failing or seized circulation pump motor can cause the frequency converter to report a fault back to the SLT. Listen for unusual noises from the pump and check for mechanical resistance or motor winding faults.

  5. 05

    Defective SLT control board

    Part replacement

    If all wiring, voltage, and downstream components test correctly, the SLT control board itself may have failed and is unable to maintain communication with the frequency converter. This is the least common cause but should be considered after other components are ruled out.

See the test procedure for each cause

Frequently asked questions about F79

What does F79 mean on a Miele dishwasher?
F79 indicates a communication fault between the circulation pump frequency converter electronic and the main SLT control board. The dishwasher requires this communication link to regulate pump speed and confirm proper operation during wash cycles. When the link fails or produces invalid signals, the machine stops and displays F79. The fault can involve the wiring harness, supply voltage, the frequency converter, or the circulation pump itself.
Can I fix F79 on my Miele dishwasher myself?
Some basic checks, such as inspecting visible wiring connectors for loose or corroded connections, are within reach for a confident DIYer. However, properly diagnosing this fault requires a multimeter to check supply voltage at the SLT terminals and the ability to evaluate electronic components. Most homeowners will benefit from having a qualified appliance technician perform the diagnosis and any component replacement.
Will resetting my Miele dishwasher clear the F79 error?
Resetting the dishwasher may temporarily clear the error code, but F79 will return if the underlying fault in the wiring, voltage supply, frequency converter, or circulation pump has not been corrected. A reset is useful for confirming whether the fault is intermittent, but it is not a repair. Persistent F79 codes require proper component-level diagnosis.
Is it safe to use my Miele dishwasher while it shows F79?
The dishwasher will typically not complete a wash cycle when F79 is active, as the machine halts operation upon detecting the fault. Attempting to force operation with a known communication fault between the control board and the pump could potentially cause further damage to electronic components. It is best to leave the machine off until the fault is diagnosed and repaired.
How much does it cost to repair a Miele dishwasher F79 error?
Repair costs vary depending on which component is at fault. A wiring harness repair or connector fix is generally less expensive, while replacing the frequency converter electronic or the SLT control board will cost more, often ranging from a few hundred dollars up to several hundred dollars including parts and labor. Getting a diagnostic assessment from a Miele-experienced technician will give you a more precise estimate based on your specific machine.

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