Furnace attempts to ignite but shuts down after a few seconds, error 102 displayed.

Safety warning: Turn off power and gas before opening the furnace. Flame loss can indicate combustion or gas supply problems.

• Observe the sequence: Restore power and gas, then call for heat. Watch through the sight glass: if the flame lights and then goes out within a few seconds, the control is not sensing a stable flame.
• Clean burner and flame sensor: Turn power and gas OFF. Remove the burner assembly cover. Clean burner ports with a soft brush and vacuum. Remove the ionization electrode and clean the rod as described above. Ensure the electrode tip is correctly positioned in the flame path per the Ariston service diagram (usually 3–5 mm above the burner).
• Check gas supply stability: Confirm other gas appliances do not flicker or go out. If they do, contact your gas supplier to check pressure.
• Inspect grounding: The control board and burner must be properly grounded for accurate flame sensing. Check the green/yellow earth wire from the furnace chassis to the supply and tighten any loose screws.
• Check condensate drain (for condensing models): A blocked condensate trap can disturb combustion. Inspect the plastic condensate trap and hose; clear any sludge and ensure free flow to the drain.

If the 102 error persists after cleaning and basic checks, the gas valve or control board may be defective and should be tested by an Ariston-certified technician.