Miele Dishwasher Error Code F78

• Dishwasher stops mid-cycle and displays F78 error code on the control panel
• Water inside the dishwasher feels cold or lukewarm during operation
• Dishes come out not properly cleaned or with residue remaining
• Error code appears during the wash or drying phase
• Dishwasher may drain prematurely when error occurs
• Control panel may beep or signal an alert when temperature threshold is not reached

• Failed heating element (most common cause in USA 120V models)
• Defective temperature sensor that incorrectly reads water temperature
• Loose or disconnected wiring harness to the heating element
• Faulty heating relay or control board component
• Lime scale or mineral buildup on heating element from hard water (common in many USA regions)
• Water inlet valve not delivering adequate water flow to heating chamber
• Tripped thermal overload protection due to heating element burnout
• Control board failure preventing proper communication with heating system

• Check your home's circuit breaker panel to ensure the breaker serving the dishwasher is in the ON position and has not tripped; if tripped, switch it OFF then back ON
• Verify the dishwasher's water supply valve (located behind or under the unit where water line connects) is fully open by turning the valve handle counterclockwise until it stops
• Open the dishwasher door and inspect the filter basket at the bottom for debris, food particles, or blockages; remove and rinse clean if needed
• Check both the upper and lower spray arms for clogs or buildup by rotating them and looking through the spray holes; use a small wire or toothpick to clear any blocked holes
• Ensure the dishwasher door is closing completely and the latch mechanism is fully engaged; listen for a solid click when shutting the door
• Perform a hard reset by turning off the circuit breaker that supplies power to the dishwasher for 60 seconds, then switching it back ON to allow the control board to reinitialize
• If error persists after these checks, discontinue use and contact a Miele-authorized service technician in your area, as internal heating element or control board repair requires professional diagnosis