Boiler displays 106, intermittent lockouts, sometimes works after reset

Safety: Isolate electrical power before accessing internal components.

• Locate flow NTC: Find the flow temperature sensor clipped or screwed onto the flow pipe or heat exchanger. Check that it is firmly attached and making good contact with the metal surface.
• Inspect wiring: Look for frayed wires, loose connectors, or signs of overheating. Reseat the plug on the PCB and at the sensor.
• Resistance check (for competent users): With power off and sensor disconnected, measure resistance with a multimeter. Compare to Ariston's temperature/resistance chart. A sensor reading open circuit or shorted should be replaced.
• Replace sensor: If faulty, fit a new genuine Ariston flow NTC sensor, ensuring correct positioning and new thermal paste or clip if required.
• Reset and test: Restore power, reset the boiler, and monitor operation. If 106 persists with a new sensor, the PCB may be at fault and requires professional diagnosis.