Ariston Oven Error Code ER99

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.

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.

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.

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.

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.