BoilerFaultCodesSime 100 Fault Code
The Sime 100 fault code means: your boiler has detected that the water pressure in your heating system is too low to operate safely.. It appears on 1 Sime model in our database.
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DIY fix possible
Locate the filling loop, which is usually a small silver braided hose with one or two valves located underneath the boiler.Open the valve(s) slowly until the pressure gauge on the front of the boiler reads between 1.0 and 1.5 bar.Close the valve(s) tightly and restart the boiler to clear the fault code.
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Sime models that show the 100 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Sime 100 fault code information on this page is sourced and cross-checked against the official Sime service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026