BoilerFaultCodesWhat the manual says
Manufacturer manualThe product is within the waiting period of the modulation block/operating block function as a result of low water pressure/water deficiency (flow/return spread too large).
DIY fix possible
Check your boiler's pressure gauge and ensure it is between 1 and 1.5 barIf the pressure is low, use the filling loop to top it up to the correct levelEnsure all your radiator valves are fully open to allow water to circulate freely
Avoid the next call-out bill
A cover plan would handle faults like S.53: no call-out fees, no surprise bills.
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Related fault codes
All 143 fault codes on the Compact
Seeing a different code? Every code this model can display, in one place.
Related guides you might find useful
Hot water works but heating does not
On a combi it is usually the diverter valve. On a system boiler, the motorised valve.
Read →What pressure should my boiler be?
1 to 1.5 bar when cold on most UK boilers, from the manuals.
Read →No hot water but heating works
Almost always a stuck diverter valve on a combi.
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