BoilerFaultCodesThe 6 most common faults
Your boiler has detected that it is running much hotter than it should be and has switched itself off to prevent internal damage.
Check that all radiator valves are fully open to allow water to flow.Ensure there is enough pressure in the system by checking the built-in gauge.Press the reset button on the front of the boiler to see if the fault clears.
Your boiler has detected that it is getting dangerously hot and has shut itself down to prevent damage.
Check that all radiator valves are fully openEnsure the boiler pressure is between 1.0 and 1.5 bar on the gaugeReset the boiler by turning the mode knob to the 'reset' position for 2 seconds
Your boiler has detected that it is becoming dangerously hot and has shut itself down to prevent any internal damage.
Check that your radiator valves are fully openEnsure your boiler pressure is between 1.0 and 1.5 bar on the gaugeReset the boiler by turning the mode knob to 'reset' and back to 'on'
Your boiler has detected that it is running much hotter than it should be and has shut itself down to prevent any internal damage.
Check that your radiator valves are fully open.Ensure your system water pressure is between 1.0 and 1.5 bar on the gauge.Restart the boiler by turning the mode knob to 'reset' and then back to 'on'.
Your boiler has stopped working because the water pressure inside the system has dropped too low to operate safely.
Locate the external filling loop, which is usually a flexible silver braided hose under your boiler.Open the valves at both ends of the hose to let mains water into the system until the pressure gauge reads between 1 and 1.5 bar.Close both valves tightly to stop the flow of water and check the gauge remains steady.
Your boiler has switched itself off for safety and is displaying this code alongside another digit to point to a specific problem.
Look at the display and wait for it to flash a second digit (e.g., L2 or L9)Check that your gas supply is active (e.g., check other gas appliances)Press and hold the 'Mode' or 'Reset' knob for two seconds to clear the lockout
on the Ideal Isar HE
Based on parts cited in our fault code database. Your engineer will confirm what's actually needed after diagnosis.
Call a Gas Safe engineer if…
- You can smell gas or see signs of a leak
- The Ideal shows an Emergency or High severity code
- The boiler keeps locking out after repeated resets
- You've tried the DIY checks and the fault hasn't cleared
- There's visible water leaking from the boiler
- The flame is yellow or orange instead of blue