Furnace will not start, display shows error 101, no ignition attempt heard.

Safety first: Turn off electrical power to the furnace at the breaker and close the gas shutoff valve before removing any covers. If you ever smell gas continuously, evacuate and contact your gas supplier or emergency services.

• Reset the unit: Restore power, ensure the room thermostat is calling for heat, and press the reset button (if present) on the Ariston control panel. Observe if the 101 code reappears.
• Check gas supply: Verify the manual gas cock near the furnace is fully open. Confirm other gas appliances in the home work properly to rule out a supply issue.
• Inspect burner area: With power and gas OFF, remove the burner access panel. Look for heavy dust, rust flakes, or debris on the main burner and around the flame electrode. Gently vacuum loose debris and clean metal surfaces with a soft brush.
• Clean the ionization electrode: Locate the flame sensing (ionization) electrode near the burner. Carefully remove it and clean the metal rod with fine emery cloth or a Scotch-Brite pad until shiny. Do not bend the rod. Reinstall and ensure the ceramic insulator is not cracked.
• Check wiring to gas valve and electrode: Inspect connectors to the gas valve coil and ionization electrode for corrosion or loose fit. Reseat any loose plugs.
• Test operation: Restore gas and power, then call for heat. Watch through the inspection window: the fan should start, then ignition, then flame. If the 101 code returns and no flame appears, the gas valve or control board may require professional diagnosis.

If you are not qualified to work with gas components, stop after cleaning and visual checks and contact an authorized Ariston service technician.