BoilerFaultCodesDaikin 11-66 Fault Code
Also written as 1166 — same fault.
The Daikin 11-66 fault code means: your boiler is struggling to light or recognize that a flame has started, causing it to shut down for safety after several failed attempts.. It appears on 1 Daikin model in our database.
Technical description: Flame Signal loss in safety time – try to reset the boiler after 3rd unsuccessful ignition
What causes the Daikin 11-66 fault?
This fault occurs when the boiler's internal sensors fail to detect a stable flame during the startup process. The most common reasons are a worn-out ignition electrode that cannot create a spark or a buildup of carbon on the probe that monitors the flame. In some cases, a blockage in the drainage pipe or a faulty gas valve prevents the burner from staying lit safely.
This fault is more common during the first cold snap of autumn when a boiler that has been idle all summer is suddenly forced to work at high intensity.
DIY fix possible
Check if other gas appliances, like a hob, are working to ensure gas is reaching the propertyCheck that your gas meter is in credit if you use a prepay meterLocate the reset button on the control panel and press it once to attempt a restart
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Gas Safe Register →Daikin models that show the 11-66 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Daikin 11-66 fault code information on this page is sourced and cross-checked against the official Daikin service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026