Boiler displays 108, no operation, pressure gauge at zero or very low

Safety: Do not run the boiler with no water; this can cause severe damage.

• Inspect for obvious leaks: Check around radiators, valves, and under the boiler for water. If a major leak is present, isolate the water supply and call a plumber.
• Refill system: Use the Ariston filling loop to slowly refill the system to 1.2–1.5 bar. Bleed radiators and the boiler's automatic air vent if accessible.
• Check filling loop valves: Ensure the valves fully close after filling. A stuck-open loop can cause overpressure and discharge from the safety valve.
• Verify gauge vs. sensor: If the gauge shows correct pressure but 108 persists, the water pressure sensor may be faulty or its pipe blocked. This usually requires an engineer to clean or replace.
• Reset: Once pressure is restored and stable, reset the boiler and test heating and hot water.