Boiler Repair & Fault Finding

• Flames burning irregular or yellow instead of a steady blue: usually incomplete combustion, needs investigating promptly.
• Smell of fumes or gas: turn off the gas at the meter and call us straight away.
• Stains or smoke marks around the boiler: a sign of poor combustion or a flue problem.
• Overheating: the temperature gauge climbing above roughly 80°C.
• Pressure dropping rapidly: needing refilling more than once a month points to a leak somewhere in the system.
• Fan whining or screeching: often a failing fan bearing.
• Pilot light going out repeatedly: commonly a thermocouple fault.
• Poor or no hot water: could be the boiler, or a diverter valve fault.
• Radiators not all heating up together, sometimes a boiler fault, sometimes just an unbalanced system that needs rebalancing.

Oil boiler faults

Oil boilers have their own common failure points. If your boiler keeps tripping the lockout button (the small red reset button on the burner unit), repeated resets are a sign of an underlying fault rather than something to keep pressing through. Common causes include a dirty or worn nozzle, an ignition electrode fault, water or debris in the fuel line, or a failing photocell. Other things we're regularly called out for: the burner firing then cutting straight out, smoke or a smell of oil around the flue, a noisy or rumbling burner, and no hot water or heating despite the burner running.

Should you repair or replace?

As a rough guide: if your boiler is under 8 years old, a repair is almost always the right call. Between 8–12 years, it's worth comparing the repair cost against a new installation: if a repair is going to cost more than roughly half the price of replacing it, replacement usually makes more financial sense. Past 12 years, a new A-rated condensing boiler will typically pay back the difference in lower fuel bills within 3–5 years, on top of being far less likely to break down on you mid-winter. We'll give you our honest recommendation either way. See our new boiler installation page if replacement makes sense.