BoilerFaultCodesTechnical description
No heating demand from external controls (clamp 3-4 open)
What causes this fault?
This code occurs when the boiler is technically ready to provide heat, but it hasn't received a signal from your external controls to start. The most common reason is that your room thermostat is set lower than the current room temperature or has run out of batteries. It essentially means the boiler is 'on standby' waiting for your timer or thermostat to tell it that the house is cold.
This is frequently reported during the first cold spell of autumn when homeowners forget to replace thermostat batteries or adjust summer timers.
DIY fix possible
Check that your room thermostat is turned up higher than the current room temperature.Ensure your heating programmer or timer is set to 'ON' or 'AUTO'.Replace the batteries in your wireless wall thermostat if the screen is blank or showing a low battery symbol.