Boiler fault code lookup

Name: TradePlanr
Rating: 5 (100 reviews)
Author: TradePlanr

What that flashing code on the display actually means. Pick your boiler brand for plain-English explanations of each fault code — the common causes, what is safe to check yourself, and when to call a Gas Safe registered engineer.

Worcester Bosch

8 codes

Greenstar combi, system and heat-only boilers. Older models show letter codes (EA, C6, A1); newer Greenstar 8000, 4000 and Lifestyle models show numeric codes on the display.

Vaillant

8 codes

ecoTEC combi, system and heat-only boilers. Vaillant shows fault codes in an F.xx format on the display (for example F.22, F.28), each pointing to a specific fault the control board has detected.

Baxi

7 codes

Baxi combi, system and heat-only boilers. Modern Baxi models show an E-prefixed numeric fault code on the display (for example E133 or E119), which pinpoints the area at fault so it can be diagnosed quickly.

Ideal

7 codes

Ideal Logic, Logic+, Vogue and Independent combi, system and heat-only boilers. Faults show as an L or F prefix followed by a number on the display (L2, F1, L1), plus a few C codes for sensor faults — the L codes are usually lockouts you can reset, the F codes are operating faults.

Popular fault codes

Worcester Bosch EA — Ignition / flame detection lockout Worcester Bosch 227 — No flame detected Worcester Bosch A1 — Pump / circulation fault (dry fire protection)Worcester Bosch C6 — Fan fault Worcester Bosch E9 — Overheat — primary temperature too high Worcester Bosch F0 — Internal / sensor fault Worcester Bosch 1017 — Low water pressure Worcester Bosch D5 — PCB / internal communication fault Vaillant F.22 — Low water pressure / dry fire protection Vaillant F.28 — Ignition failure on startup Vaillant F.29 — Flame loss during operation Vaillant F.75 — Pump / water pressure sensor fault Vaillant F.27 — Flame simulation / residual flame detected Vaillant F.62 — Delayed gas valve shut-off (gas valve fault)Vaillant F.72 — Flow / return temperature sensor fault Vaillant F.20 — Safety cut-out / overheat Baxi E133 — Gas supply fault / ignition lockout Baxi E119 — Low water pressure Baxi E110 — Overheat — primary circuit too hot Baxi E125 — Circulation fault Baxi E28 — Flue gas (NTC) thermistor fault Baxi E160 — Fan fault Baxi E131 — Flue gas thermostat / flue safety device Ideal L2 — Ignition lockout / flame loss Ideal F2 — Flame loss / no flame detected Ideal F1 — Low water pressure Ideal L1 — No / low water flow — circulation fault Ideal C2 — Sensor fault (thermistor out of range)Ideal F3 — Fan fault Ideal L5 — Fan speed / fan lockout fault

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