Combi Boiler Pilot Light or Ignition Won't Stay Lit

Most modern combi boilers use electronic ignition rather than a standing pilot, but the symptom is the same: the boiler clicks and tries to light but the flame won't establish or hold. This points to the ignition electrode, flame sensor, gas supply or gas valve.

Ignition work is gas work — leave it to a licensed gas fitter. If you smell gas at any point, treat it as an emergency.