Main Fault Codes

Select a fault code to see its meaning, common causes and how to fix it.

E09 The E09 fault code on Main boilers (also seen on Baxi and Potterton boilers, which share the same BDR Thermea control… Read more →
E109 The E109 code on Main boilers indicates a pre-circulation fault — the boiler has detected inadequate water flow through… Read more →
E110 The E110 code on a Main (Eco Compact) boiler means the overheat safety thermostat has activated and shut the boiler… Read more →
E118 The E118 code appears on Main boilers (and the closely related Baxi and Potterton ranges, which share the same fault… Read more →
E119 The E119 fault code indicates that your Main boiler has detected water pressure that has dropped too low to operate… Read more →
E125 The E125 code on a Main boiler signals a primary circulation fault — the boiler's PCB has detected that water is not… Read more →
E128 The E128 fault code on Main boilers signals a repeated flame failure lockout. The boiler monitors every ignition… Read more →
E130 The E130 code on a Main Heating boiler means the flue safety thermostat has tripped because the boiler detected an… Read more →
E133 The E133 fault code on a Main boiler indicates that the boiler attempted to light but failed to establish a flame,… Read more →
E135 The E135 code on Main boilers indicates that the boiler has shut itself down — locked out — after detecting a problem… Read more →
E154 When your Main boiler displays E154, it has detected a problem during its internal flow and return sensor temperature… Read more →
E160 The E160 code on a Main boiler indicates that the boiler's control system has detected a problem with the flue fan —… Read more →
E168 The E168 is Main's catch-all lockout code — sometimes called the 'mystery code' — because it doesn't point to a single… Read more →
E20 The E20 fault code on a Main boiler signals a problem with the central heating NTC (Negative Temperature Coefficient)… Read more →
E270 The E270 fault code on Main boilers signals a circulation fault — sometimes described as a 'dry fire' condition — where… Read more →
E28 The E28 fault code on Main boilers indicates a problem with the flue thermistor — a small NTC (Negative Temperature… Read more →
E321 The E321 code on a Main boiler indicates that the boiler's control system has detected a problem with the hot water NTC… Read more →
E384 The E384 fault code indicates that the boiler's PCB (printed circuit board) has detected a 'false flame' signal —… Read more →
E40 The E40 fault code on Main boilers (which share their fault code platform with Baxi boilers) indicates a problem with… Read more →
E50 The E50 code appears on your Main boiler display (shown as 'E' followed by '50') when the control board detects a… Read more →
E60 The E60 code on Main boilers most likely indicates a fault related to the fan, air pressure switch, or flue sensor… Read more →
E83 The E83 fault code on Main boilers signals a 'No Communication' error — the boiler's internal electronics have lost the… Read more →