Boiler fault codes by make: a high-level guide to reading your display

Reading fault codes across different makes: the short technical version

Worcester Bosch combi and system boilers typically show letter-number codes such as EA or E9, covering ignition and overheat faults respectively. Vaillant's ecoTEC range uses F-prefixed codes, with F22 and F28 among the most commonly seen, covering water content and ignition failure. Ideal's Logic and Vogue ranges use short L and F codes such as L2 or F2, again splitting broadly into flame-loss and overheat categories. Baxi's Duo-tec and related ranges display E-prefixed numeric codes, such as E110 or E119, for overheat and pressure faults respectively. Glow-worm, part of the same group as Vaillant, follows a similar F-code pattern. On the oil side, Grant, Firebird and Warmflow appliances tend to use simpler lockout indicator lights or basic display codes rather than the detailed digital libraries seen on gas combis, reflecting the more mechanical nature of an oil burner control box. Across every make, the same principle holds: two reset attempts is the sensible limit, and a code that returns needs a qualified engineer rather than further resets, Gas Safe registered for any gas appliance and OFTEC-registered for any oil appliance.

Key points on reading fault codes across different makes

• Worcester Bosch: letter-number codes, e.g. EA (ignition), E9 (overheat)
• Vaillant and Glow-worm: F-prefixed codes, e.g. F22 (water), F28 (ignition)
• Ideal: short L and F codes, e.g. L2 (flame loss), F2 (overheat)
• Baxi: E-prefixed numeric codes, e.g. E110 (overheat), E119 (pressure)
• Grant, Firebird and Warmflow oil burners: simpler lockout lights over detailed codes

Questions we get asked

Do all boilers show a fault code on screen?

No. Many older boilers, and most oil burner control boxes, use a simple lockout light or reset button rather than a digital code display.

Is it worth looking up my exact code online before calling?

It can help you describe the fault, but codes for the same symptom vary by model year even within one manufacturer, so treat any online guide as background rather than a diagnosis.

Should I reset the boiler if I do not recognise the code?

Two attempts is generally the accepted limit for any make. If it locks out again, stop and book an engineer rather than continuing to reset it.

Does the make of my boiler affect how quickly it can be fixed?

Not usually, provided the correct diagnostic approach is used for that manufacturer's system and parts availability is checked in advance.

Extra detail on reading fault codes across different makes

Across our BA1 to BA5 and BS39/BS40 coverage we service a genuine mix of all of these makes, and the pattern holds regardless of brand: noting the exact code or light pattern, and whether the boiler attempted to fire at all, does more to speed up a visit than trying to self-diagnose from a code lookup alone.

Where we deal with this

• West Pennard (BA6) · 13 mi
• Paulton (BS39) · 3 mi
• Chew Magna (BS40) · 8 mi