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Error code reference

Ariston Oven Error Code ER99

Invalid error code received from power supply board or error code not applicable to this appliance.

Ariston codesAriston oven codes

Invalid error code received from power supply board or error code not applicable to this appliance.

First step from the service manual

Replace the power supply board.

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

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What ER99 means on a Ariston oven

ER99 on an Ariston oven indicates that the main control board has received an error code from the power supply board that it cannot recognize or interpret. Rather than a specific component failure mapped to a known fault, this code signals a communication breakdown where the data transmitted by the power supply board falls outside the expected error code range for this particular appliance model. In other words, the power supply board is sending a signal, but the control system has no defined response for it.

This situation typically points to a fault originating in the power supply board itself. The board may be generating corrupted or erroneous output due to internal component failure, such as a failing capacitor, degraded voltage regulation, or a logic fault on the board. It is also possible that an incorrect or incompatible power supply board has been installed at some point, causing a mismatch between the error reporting protocol of the board and the expectations of the main control system.

Because the error originates at the power supply board level, diagnostic effort should be focused there first. Inspecting wiring connections between the power supply board and the main control board for loose, corroded, or damaged terminals is a reasonable preliminary step. However, given the nature of ER99 as an unrecognized code, the primary resolution path is replacement of the power supply board. Attempting to clear the code without addressing the board is unlikely to produce a lasting fix.

Source: manufacturer service documentation.

Common causes of ER99

  1. 01

    Failed power supply board

    Part replacement

    Internal failure of the power supply board, such as degraded capacitors or a logic fault, causes it to transmit an unrecognized error code to the main control board. This is the primary cause identified for ER99 and the first component to replace.

  2. 02

    Incompatible or incorrect power supply board

    Part replacement

    If a replacement power supply board was previously installed, it may not be the correct version for this specific Ariston oven model, leading to a protocol mismatch in error reporting that triggers ER99.

  3. 03

    Loose or corroded wiring between boards

    Wiring / connection

    Poor connections on the wiring harness linking the power supply board to the main control board can cause corrupted signal transmission. Inspect connectors for corrosion, pushed-back pins, or loose seating before replacing parts.

  4. 04

    Main control board communication fault

    Part replacement

    In less common cases, the main control board itself may have a reception or processing fault that causes valid signals from the power supply board to be interpreted as unrecognized codes. This is considered only after the power supply board has been replaced and the error persists.

See the test procedure for each cause

Frequently asked questions about ER99

What does ER99 mean on a Ariston oven?
ER99 means the oven's main control board has received an error signal from the power supply board that it cannot identify or match to any known fault for this appliance. It indicates a communication or compatibility issue originating at the power supply board. The code itself is flagged as invalid or not applicable to this model, which points directly to a problem with the power supply board sending the signal.
Can I fix ER99 on my Ariston oven myself?
A knowledgeable DIYer can start by checking that all wiring connectors between the power supply board and the main control board are fully seated and free of corrosion. However, the recommended fix is replacement of the power supply board, which involves working inside a high-voltage appliance. If you are not comfortable working around mains voltage components, this repair is best left to a qualified technician.
Is it safe to use my Ariston oven when ER99 is displayed?
ER99 indicates a fault in the internal power supply board, which means the oven's power management may not be operating correctly. Using the oven in this state is not recommended, as the underlying fault could affect performance unpredictably. The appliance should be inspected and the faulty board replaced before regular use resumes.
Will resetting my Ariston oven clear the ER99 error?
A power cycle or reset may temporarily clear the display, but ER99 is caused by an underlying fault in the power supply board, not a transient software glitch. If the board is failing or incompatible, the error will return. A reset alone is not a reliable fix and the power supply board should still be inspected and replaced.
How much does it cost to repair an Ariston oven showing ER99?
Repair costs depend on parts availability and whether you hire a technician or replace the board yourself. A replacement power supply board typically costs in the range of $80 to $200 or more depending on the specific model. Adding professional labor for diagnosis and installation can bring the total repair cost to somewhere between $150 and $350 or higher, depending on your location and service rates.

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