Boiler troubleshooting guides

History The History of the Boiler and Central Heating

Boiler radiators warm at the bottom but cold at the top (all brands)

Radiator is warm at the bottom but stays cold across the top

Boiler completely dead, no display or lights at all (all brands)

Boiler shows absolutely no display or lights at all

Boiler losing pressure repeatedly (Worcester Bosch, Ideal & Vaillant)

Boiler pressure gauge keeps dropping below 1 bar, needing regular repressurising

Boiler heats water but radiators stay cold (Worcester Bosch & Baxi)

Hot water works fine but the central heating radiators stay cold, or vice versa

Boiler keeps locking out or won’t fire up (Ideal, Vaillant, Vokera, Glow-worm & Potterton)

Boiler shows a fault code or simply won't ignite when heating or hot water is called for

Worcester Bosch EA fault code — boiler won’t ignite or loses flame

Display shows EA and the boiler won't ignite or loses flame during operation

Worcester Bosch D5 fault code — condensate pipe or pump issue

Display shows D5 and the boiler has locked out

Vaillant F.28 and F.29 fault codes — ignition failure or flame loss

Display shows F.28 or F.29 and the boiler has locked out

Vaillant F.22 and F.75 fault codes — low pressure or pump sensor fault

Display shows F.22 or F.75

Boiler making a loud banging or “kettling” noise (all brands)

Loud banging, rumbling, or kettle-like noise when the boiler fires