Boiler Fault Code Guide

WHAT YOUR BOILER FAULT CODE MEANS

Manufacturer-specific fault-code guides for Vaillant, Worcester Bosch, Ideal and Baxi boilers. Some codes you can fix yourself in a minute; the rest need a Gas Safe engineer — and we can have one at your door today.

Vaillant

5 codes

F22

Low system water pressure — the boiler has shut down as pressure has fallen below 0.6 bar.

Vaillant fault

F23

Dry-fire protection — the boiler has shut down to prevent damage from running without enough water.

Vaillant fault

F27

False flame signal — the boiler thinks a flame is present when no gas is burning.

Vaillant fault

F28

The boiler has failed to ignite after several attempts.

Vaillant fault

F75

The boiler can't detect pressure change when the pump starts — pump or pressure-sensor fault.

Vaillant fault

Worcester Bosch

4 codes

Ignition fault — the boiler failed to detect a flame after attempting to light.

Worcester Bosch fault

Burner shut down during operation — the flame went out while the boiler was running.

Worcester Bosch fault

Safety thermostat / overheat limit has tripped.

Worcester Bosch fault

Hot-water (DHW) temperature sensor fault.

Worcester Bosch fault

Ideal

3 codes

Ignition lockout — the Ideal boiler failed to light.

Ideal fault

Flame loss during operation — the burner went out while running.

Ideal fault

Ignition lockout — the Ideal boiler couldn't establish a flame.

Ideal fault

Baxi

3 codes

128

Flame loss during operation — the burner flame went out while running.

Baxi fault

133

Ignition failed — the Baxi boiler couldn't light.

Baxi fault

E119

Low system water pressure — the Baxi has shut down below 0.5 bar.

Baxi fault

BOILER FAULT CODES — QUICK HELP

What should I do if my boiler displays a fault code?

Note the exact code shown on the display, then find it on this page. Some codes (like Vaillant F22 or Baxi E119) are low-pressure warnings you can fix yourself in a minute; others are gas-related and need a Gas Safe engineer. Always check your gas supply first.

Can I fix a boiler fault code myself?

Only a few — typically low-pressure warnings (repressurise via the filling loop) and, in freezing weather, a thawed condensate pipe. Anything involving gas, ignition, flame sensing or the flue must be done by a Gas Safe registered engineer.

How much does a boiler engineer call-out cost in Glasgow?

Central Heating Scotland charges transparent, fixed call-out fees across Glasgow and Renfrewshire. Where possible we quote the repair cost before starting work. Call 0141-374-0987 for a same-day engineer to your postcode.

Are boiler fault codes the same on every brand?

No. Vaillant, Worcester Bosch, Ideal and Baxi use different code systems — Vaillant uses F-codes, Worcester often uses letters (EA, EB), Baxi mixes numbers and 'E' codes. Use the brand lists below to find the exact meaning for your boiler.

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