High
Section G on Alpha 240XE

Your boiler is struggling to control how much heat it produces, which likely means it cannot sustain a steady temperature for your radiators or hot water.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description

Burner output does not modulate (Main PCB plug connections, modulating coil faulty, or Main PCB terminals 41, 42)

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

Find a Gas Safe engineer
Search the official register →

Related guides you might find useful

No hot water but heating works

Almost always a stuck diverter valve on combis.

Read →

Pilot light keeps going out

Older boilers — thermocouple, draught, gas supply.

Read →

Radiators cold at the bottom

Sludge build-up — needs flushing, not bleeding.

Read →