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Error code reference

Ariston Oven Error Code ER78

Key5 fault on Touch control

Ariston codesAriston oven codes

Key5 fault on Touch control — touch button malfunction.

First step from the service manual

Open door, wait for condensation to dry; if fault persists and all inductive rubber pieces are present, replace display board.

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

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What ER78 means on a Ariston oven

ER78 indicates a Key5 fault on the touch control system of the Ariston oven. This error is generated when the control board detects an anomaly with the fifth touch-sensitive button on the display panel. The touch control system relies on inductive rubber contact pieces positioned beneath or around each button zone to register valid input. When Key5 behaves erratically, reads as continuously pressed, or fails to register at all, the control logic flags this fault and displays ER78.

The most frequent trigger for this error is moisture or condensation accumulating on or near the touch panel surface. Steam from cooking can settle on the glass or seep into the panel area, creating false capacitive readings that the control board interprets as a stuck or malfunctioning button. This is why the first diagnostic step is to open the oven door and allow adequate time for any trapped moisture to evaporate before concluding that a hardware failure has occurred.

If the error persists after drying, a physical inspection of the inductive rubber contact pieces is essential. These small components sit beneath the touch surface and are critical to accurate button detection. If any are missing, displaced, or degraded, Key5 will malfunction regardless of board condition. Only when these pieces are confirmed to be fully intact and correctly positioned should the display board itself be considered the root cause and replaced.

Source: manufacturer service documentation.

Common causes of ER78

  1. 01

    Condensation or moisture on the touch panel

    Wiring / connection

    Steam from cooking can settle on or behind the touch control surface, creating false readings on Key5. Opening the oven door and allowing the panel to dry fully often resolves the fault without any parts replacement.

  2. 02

    Missing or displaced inductive rubber contact piece

    Part replacement

    The touch system depends on small inductive rubber pieces positioned at each button location. If the Key5 rubber piece is absent, out of position, or degraded, the button cannot register input correctly and will trigger ER78.

  3. 03

    Damaged or faulty display board

    Part replacement

    If moisture has been ruled out and all inductive rubber pieces are present and correctly seated, the display board itself may have failed internally at the Key5 circuit. Replacement of the display board is the recommended corrective action in this scenario.

  4. 04

    Physical damage to the touch surface or panel

    Part replacement

    Cracks, chips, or heavy soiling on the touch panel glass or overlay can interfere with capacitive sensing at the Key5 position. Inspect the panel surface closely for visible damage or buildup that could be disrupting the button zone.

See the test procedure for each cause

Frequently asked questions about ER78

What does ER78 mean on a Ariston oven?
ER78 indicates a Key5 fault on the Ariston oven's touch control panel, meaning the fifth touch button has been detected as malfunctioning. The control board monitors all touch inputs continuously and flags this code when Key5 produces an unexpected or invalid signal. Moisture from cooking is the most common cause, but a missing inductive rubber contact piece or a failed display board can also be responsible.
Can I fix ER78 on my Ariston oven myself?
The first step is something any user can do: open the oven door and allow time for condensation to dry from the touch panel, then check if the error clears on its own. If it persists, inspecting the inductive rubber contact pieces requires opening the panel area, which is best handled by a technician. Replacing the display board is also a technical repair that involves working with internal wiring and components.
Is it safe to use my Ariston oven while ER78 is displayed?
ER78 relates to a touch button fault on the control panel rather than a heating or gas system failure, so the immediate safety risk is limited. However, a malfunctioning control interface could prevent you from adjusting settings or shutting off functions reliably. It is advisable to avoid extended use until the fault is diagnosed and resolved.
Will resetting the oven clear the ER78 error code?
A power reset may temporarily clear the display, but if the underlying cause, such as moisture, a missing rubber contact piece, or a faulty display board, has not been addressed, the ER78 code is likely to return. Drying the panel thoroughly before resetting gives the best chance of a lasting resolution without parts replacement.
How much does it cost to repair an Ariston oven showing ER78?
If the fault is caused by condensation alone, there is no parts cost involved. Replacing an inductive rubber contact piece, if available separately, would be a low-cost repair, typically in the range of a few dollars for the part plus labor. A full display board replacement is the most expensive scenario, with parts and labor costs commonly ranging from around 100 to 300 dollars depending on the specific model and technician rates in your area.

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