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Error code reference

Miele Dishwasher Error Code F51

Heater pressure switch fault

Miele codesMiele dishwasher codes

Heater pressure switch fault — one second after program start, heater relay K1/1 is activated and if the electronic receives no power through the heater pressure switch contacts, F51 is stored.

First step from the service manual

Check heater relay; replace if contacts are open or solenoid is defective.

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

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What F51 means on a Miele dishwasher

The F51 error code on a Miele dishwasher indicates a heater pressure switch fault. Specifically, the control board activates heater relay K1/1 approximately one second after a wash program begins. At that point, the electronic control expects to receive a confirmation signal back through the heater pressure switch contacts. If that signal does not return, the fault is logged as F51. This tells the technician that the circuit between the relay and the pressure switch is broken, or that one of those components has failed.

The heater relay K1/1 is the most likely starting point for diagnosis. Relay contacts can fail in an open state due to electrical arcing, corrosion, or age-related wear, preventing current from passing through the circuit even when the relay coil is energized. If the relay coil itself is defective, the contacts will never close at all, producing the same result. The heater pressure switch is also a key suspect, as its internal contacts can fail or become stuck open, breaking the confirmation signal back to the board.

A systematic approach to diagnosing F51 involves checking the heater relay first, inspecting its contacts for signs of burning or corrosion, and testing the coil for proper resistance. If the relay checks out, the heater pressure switch should be tested for continuity under operating conditions. Wiring between these components should also be inspected for loose connections, breaks, or corrosion that could interrupt the circuit.

Source: manufacturer service documentation.

Common causes of F51

  1. 01

    Failed heater relay K1/1 contacts

    Part replacement

    The relay contacts can fail in an open position due to arcing, corrosion, or wear, preventing the circuit from completing. Inspect the relay contacts visually for burn marks and test for continuity when the relay is energized.

  2. 02

    Defective heater relay coil

    Part replacement

    If the relay solenoid coil is open or shorted, the relay will never activate its contacts regardless of the control board signal. Test the coil resistance and compare it to expected values.

  3. 03

    Faulty heater pressure switch

    Part replacement

    The heater pressure switch contacts can fail open, meaning the confirmation signal never reaches the electronic control. Test the switch for continuity under normal operating conditions to confirm failure.

  4. 04

    Wiring or connection fault

    Wiring / connection

    Loose terminals, corroded connectors, or broken wires between the relay and the heater pressure switch can interrupt the circuit and trigger F51. Inspect all connections along this circuit path carefully.

See the test procedure for each cause

Frequently asked questions about F51

What does F51 mean on a Miele dishwasher?
F51 indicates a heater pressure switch fault. One second after a program starts, the control board activates heater relay K1/1 and then checks for a return signal through the heater pressure switch contacts. If that signal is absent, F51 is stored. The fault points to a failure in the relay, the pressure switch, or the wiring between them.
How do I fix the F51 error on my Miele dishwasher?
Start by inspecting heater relay K1/1 for open or damaged contacts and test the relay coil for proper function. If the relay is working correctly, test the heater pressure switch for continuity. Also check all wiring and connectors in the circuit for corrosion or loose terminals. Replace whichever component has failed to resolve the fault.
Is it safe to use my Miele dishwasher while F51 is showing?
It is not recommended to continue running the dishwasher with an active F51 fault. The error indicates that the heater circuit is not functioning as expected, which means the machine may not heat water properly and could behave unpredictably. Have the fault diagnosed and repaired before using the appliance again.
Will resetting my Miele dishwasher clear the F51 error?
Resetting the dishwasher may temporarily clear the displayed fault code, but F51 will return as soon as another cycle starts if the underlying component failure has not been repaired. The control board will repeat its relay and pressure switch check at program start and store the fault again if the circuit is still open.
How much does it cost to repair a Miele dishwasher F51 error?
Repair costs depend on which component has failed. A heater relay is generally a lower-cost part, while a heater pressure switch or labor for wiring repairs can add to the total. Overall repair costs typically range from around $100 to $350 or more depending on parts needed and local labor rates.

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